Contents:
[Document Version: 2.77] [Last Updated: 05/25/1998]
Notes on the Troubleshooting and Repair of Video Cassette Recorders
This F.A.Q. is (c) 1994-1998 to it's author, Samuel M. Goldwasser. All rights
reserved.
Note: A version of this document and "VCR First Aid" may also be found at the VCR Flashbook: Interactive VCR Manual web site. The content is similar but you might prefer the style of that web page. Think back 20 years. You went to the theater to see a movie. You watched TV programs when they were broadcast (there was no cable, remember?) or you missed them. TV studios and industry had video recording equipment but it was expensive and cumbersome. Little did you realize at the time, but after some false starts, the modern video revolution was about to be born. Are we better off? Whatever you decide, there is no going back. You may be able to leave your VCR's clock flashing 12:00 but you cannot escape the impact that this technology has had on so many aspects of your life. The video cassette recorder is a wonderful example of extremely complex precision technology that has been made affordable through mass production. In general, it is usually quite reliable. Treat a modern VCR with a bit of respect and it will provide trouble free service for a long time. Unlike a TV where the power circuits take their toll on circuit components, the electronics in VCR are generally quite reliable and rarely fail. Most VCR problems are mechanical - dirt and dust in the tape path, deteriorated rubber parts, dried lubrication, wear of precision parts including the spinning video heads, and abuse caused by rocks, toys, and peanut butter and jelly sandwiches.
Note: for VCR emergencies that just cannot wait, the solution may be found in the document: "VCR First Aid" and you may not need to read further. "VCR First Aid" deals with the half dozen or so acute problems that may tempt you to throw something through the window - or worse. Even if you are a technoklutz who lets your kids change the light bulbs in your house and would never consider tackling any actual repair or internal maintenance of your VCR, some basic awareness of the principles of video recording and the likely causes for common problems will enable you to intelligently deal with the service technician. You will be more likely to be able to recognize if you are being taken for a ride by a dishonest or just plain incompetent repair center. For example, did you know that one of the most dreaded of problems - the tape eating VCR - can often be remedied by a thorough cleaning and a 50 cent rubber tire? This document will provide you with the knowledge to deal with over 85% of the problems you are likely to encounter with your VCRs. It will enable you to diagnose problems and in most cases, correct them as well. First and foremost are the techniques for cleaning of the tape path and replacement of rubber parts like belts, tires, and the pinch roller - the solution to many common problems with VCRs. With minor exceptions, specific manufacturers and models will not be covered as there are so many variations that such a treatment would require a huge and very detailed text. Rather, the most common problems will be addressed and enough basic principles of operation will be provided to enable you to narrow the problem down and likely determine a course of action for repair. In many cases, you will be able to do what is required for a fraction of the cost that would be charged by a repair center. Should you still not be able to find a solution, you will have learned a great deal and be able to ask appropriate questions and supply relevant information if you decide to post to sci.electronics.repair. It will also be easier to do further research using a repair text such as the ones listed at the end of this document. In any case, you will have the satisfaction of knowing you did as much as you could before taking it in for professional repair. With your new-found knowledge, you will have the upper hand and will not easily be snowed by a dishonest or incompetent technician.
While VCRs with new convenience features are constantly introduced, the basic function of playing a tape has not changed significantly in 20 years. Even the introduction of HQ about 10 years ago does not represent a dramatic improvement. Therefore, unless you really do need a quick start transport, a real-time counter, index search, or the like, repair may not be a bad idea. The older VCRs are built much more solidly than the $150 models of today. Even high end VCRs may be built around a poorly designed transport and flimsy chassis. Many older VCRs - for example 10 year old Panasonic models (and their clones) can be kept functional - nearly indefinitely, it would seem - at minimal cost. If you need to send or take the VCR to a service center, the repair could easily exceed half the cost of a new VCR. Service centers may charge up to $50 or more for providing an initial estimate of repair costs but this will usually be credited toward the total cost of the repair (of course, they may just jack this up to compensate for their bench time). If you can do the repairs yourself, the equation changes dramatically as your parts costs will be 1/2 to 1/4 of what a professional will charge and of course your time is free. The educational aspects may also be appealing. You will learn a lot in the process. Thus, it may make sense to repair that old clunker so the kids will have their own VCR or you will have a convenient means of copying tapes (legally, of course). BTW, if you ARE one of those individuals (and there are bucket loads) who doesn't bother (or doesn't know how) to set the clock on your VCR, there is a solution - at least the next time you need to purchase a new VCR. These machines search for a TV station that includes the time code in its transmission format (it is in the vertical blanking interval should you care) and automagically sets the VCR's clock from that information. There - no more flashing 12:00! Many VCRs have this feature nowadays.
Modern VCRs - both consumer and professional - are based on what is known as helical scan recording. The main technological challenge that confronted the designers of early video recording machines was achieving the necessary bandwidth - several MHz - to faithfully capture the high frequency video signal. The first such machines ran normal audio tape past stationary recording heads at high speed - 10s of feet per second - in an attempt to solve this problem. Needless to say, the mechanisms were complex, a finite length of tape could only record a few minutes of video, and the heads wore out almost as quickly. If anything - anything at all - went wrong with the tape transport, you were up to your eyeballs is spilled tape. An alternative technology was clearly needed. Prior to practical video tape recording, the only way to preserve a TV show was to use special equipment that essentially made a film of it off of a video monitor. The quality of such recordings was not very good, editing was difficult, the film needed to be developed so playback was not immediate, and of course, the film could not be erased and reused. The first successful commercial video tape recorder was introduced around 1956 with the Ampex Quadplex - a $50,000 machine using 2 inch open reel tape and a high speed spinning head with 4 pickups rotating across the tape. This event revolutionized commercial broadcasting. However, this technology was much too complex, cumbersome, and expensive for consumer use and has a number of technological disadvantages as well. For a consumer video tape recorder to be successful it was felt that the following three major hurdles had to be overcome: * Tape loading had to be simple and foolproof using a cassette - none of this open reel stuff. * A cassette had to hold at least an hour of color video. * The cost to the consumer had to be less than $1000 (1970's dollars!) for the machine and perhaps $20 per hour for the tape. The rotating heads of the Quadplex machine provided the needed tape-head speed to achieve sufficient video bandwidth. However, the transport was much too complex for a consumer machine. Another disadvantage was that since a video frame consists of many adjacent tracks on the tape (16), special effects like stop motion as well as forward and reverse search were not possible without a frame store. While this would not be out of the question today, the cost of such a device in the 1950's would necessitate the consumer taking out a second mortgage to pay for it. Finally, the 2 inch wide format required too much tape for achieving a cost effective 1 hour program time and made the design of a manageable cassette an impossibility. A separate room would be needed to house a modest size video tape library! Helical scan overcomes most of these problems. Rather than scanning across the tape, the tape is wrapped a bit over 180 degrees around a rotating drum at a slight angle. Thus, successive tracks are written diagonally across the tape and can thus be much longer than the width of the tape as in the Quadplex. The tape, therefore can be rather narrow. The first helical scan tapes used a 1 inch format but narrower tape soon followed. The most common formats today are forms of VHS (and BETA) at 1/2", and 8 mm (mostly used for portable applications in camcorders and data storage.) 4 mm tape is used for high quality audio (DAT) as well as data storage.
Most of the following discussion unless otherwise noted applies to the VHS format. Beta, which preceded VHS into the marketplace and which has all but disappeared for consumer VCRs is actually a somewhat better system technologically with superior picture quality. However, Sony's licensing practices with respect to BETA made it inevitable that VHS would triumph in the marketplace. Too bad in some ways. Each track corresponds to 1 field of the interlaced video format. Generally, two heads opposite each other on the rotating head drum are used. One rotation of the drum corresponds to a complete video frame with heads designated A and B for the even and odd fields respectively. What this also provides is the ability to easily implement a variety of special effects including freeze frame, and fully variable speed forward and reverse motion with a recognizable and in many cases, quite clear picture. With relatively minor restriction, this becomes as simple as moving the tape forward or backward or keeping it stationary. For a not too terrible ASCII diagram and additional discussion, also see the section: "VHS physical tape format". (Camcorders and other compact systems may use 2 pairs of identical heads where the opposing pairs are separated by 270 instead of 180 degrees. This permits the use of a smaller, lighter video drum.) The A and B heads are not identical either. Their azimuth angle differs being +6 degrees for one and -6 degrees for the other. This is one of several techniques used to minimize crosstalk between adjacent tracks. Azimuth angle is how far the head gap is from being perfectly perpendicular to the direction of tape-tape motion. For example, a head with an azimith such as / will ignore most of the information recorded with an azimith of \. Note that the head gap - the distance between pole pieces - is on the order of 1 um - 1/25,000 of an inch. As a point of reference, a human red blood cell is about 7 um in diameter and an average sheet of typing paper is about 100 um in thickness. The gap is filled with a nonmagnetic material to prevent it from getting clogged and to force the magnetic flux out of the head structure and into the tape magnetic coating. This remarkably fine spacing is necessary to achieve the multimegahertz video bandwidth. Actual tape motion for a VCR is remarkably slow. To someone familiar with audio decks, the tape in a VCR even at SP speed (the fastest) seems to be crawling along. Their first reaction is often one of: "there must be something wrong as the tape is moving sooo slooowly." Nope, just amazing technology. The SP speed of a VHS VCR corresponds to a linear tape speed of only 1-5/16 ips - slower than for an audio cassette deck (1-7/8" ips). EP speed is 1/3 of this - 7/16 ips. However, the effective tape speed as seen by the video heads is over 15 feet per second due to the spinning video head drum. The luminance (Y) and color (C) components of the composite video signal are recorded differently. Luminance, which is in effect the black and white picture with all the high resolution components but no color, is frequency modulated on a carrier at around 3.4 MHz. The deviation is about 1 Mhz and the maximum frequency recorded on a VHS tape is a little over 5 Mhz (BETA is slightly different and S versions of BETA and VHS extend some of these to achieve higher bandwidths. The color signal is separated from the composite video and is amplitude modulated on a 629 KHz carrier. This is called the color under' system. The 'U' in U-Matic, a very popular industrial VCR 3/4" format (which predates Beta and VHS and is still in use) stands for this.
Sound for the VHS format is not merged into the video signal on the tape. For non-HiFi VHS VCRs, a separate stationary tape head is responsible for the audio signal. Due to the very slow tape speed, audio quality is not even comparable to a cheap audio cassette player even at the SP speed. VHS HiFi overcomes this by FM recording of the audio signal deep in the tape (recorded by a separate set of HiFi heads just before the video information), actually buried under the video information. The left and right audio channels are recorded in separate frequency bands - centered around 1.3 and 1.7 Mhz respectively. The azimuth angles for the HiFi audio heads are +/- 30 degrees which minimizes crosstalk between the recorded HiFi audio and video information. Since the head-tape speed for the VHS audio track is the same high rate as for the video track and exceeds that of a typical audio cassette deck by a factor of more than 100, VHS HiFi audio reproduction - frequency response, signal to noise ratio, and dynamic range - is excellent and approaches that of a CD. In fact, using a T120 video cassette in EP (SLP, 6 hour) mode simply to record stereo music (with the video ignored or blanked) is extremely cost effective. What other media/technology will store a 6 hour concert with nearly perfect reproduction for under $2? (Note: if you do this, some VCRs will require some kind of video input to maintain stable tape speed. You can just ignore the video portion on audio playback.) There are two disadvantages to VHS HiFi, however: (1) there may be some degradation of video quality due to unavoidable interactions with the buried audio, and (2) it is not possible to rerecord (dub) only the audio without disturbing the video.
Linear tape motion and head drum rotation must be precisely synchronized during record, play, and special effects play modes. The general functioning is similar for all but the source of the basic reference signal differs for play and record. Some of the specific relationships may differ depending on the specific VCR design. Record: reference signal is vertical sync pulse from video input: * Head drum rotation is phase locked to vertical sync pulse so that appropriate head (of the A-B pair) is in contact with the tape during the appropriate video field. * The speed of the capstan which moves the tape through the transport is also locked to the vertical sync pulses so that the selected linear tape speed (SP, LP, EP) is maintained. * Control pulses (30 Hz for US NTSC) are recorded along the bottom edge of the tape by a stationary control head. Play: reference signal is timing pulse derived from quartz oscillator: * Capstan rotation speed is locked to a 30 Hz pulse derived from a precise quartz crystal oscillator. Head drum rotation is phase locked to the control pulses now being read off of the tape by the Control head. * The tracking control is used to adjust the relative phase of the head drum with respect to the control pulses. This permits the head path across the tape to be aligned with the actual recorded tracks.
For CUE (fast play forward) and REV (fast play reverse), the capstan speed is phase locked to a multiple of the control track. Since the video heads are crossing multiple tracks during these modes, some noise bars are unavoidable. At SP speed, special wide or dual azimith heads are required to minimize this degradation. Thus, only 4 head VCRs can play SP tapes at fast speeds with minimal noise. With EP speed, the tracks actually overlap and a normal video head is wide enough to pick up enough signal from adjacent tracks to produce a mostly noise free picture. Due to the way adjacent tracks line up with LP speed, most of these special effects cannot be used due to serious tearing of the picture. The sophisticated processing needed for proper support at LP speed is generally not included in modern VCRs due to the apparent lack of interest in the LP speed (recording support at LP speed seems to be absent in more and more newer VCRs though they will all play back LP tapes at normal playback speed). Really slow speed is usually implemented as a variable frame advance with the tape fully stopping between frames. Special sets of video heads provide the best quality. Freeze frame (PAUSE) uses the same set of heads. As with CUE and REV, acceptable picture quality is provided even with a 2-head VCR for EP speed recorded tapes. In all cases, picture quality can be further improved through the use of a digital frame store. Note that the servo systems in consumer VCRs are rarely precise enough to implement the kind of instantaneous forward or reverse frame advance that is present in high performance (and high cost) editing decks having jog shuttle knobs with instantaneous and precise response.
The books listed in the section: "Popular books on VCR maintenance and repair" include additional information on the theory and implementation of the technology of video recording and VCRs. For an on line introduction to video recording technology, check out the Philips/Magnavox Electronics Reference WEB site. There you will find links to a number of articles on the basic principles of operation of CD players, laserdisc and optical drives, TVs, VCRs, cassette decks, loudspeakers, amplifiers, satellite receivers, and other consumer A/V equipment. For some information on helical scan audio and data recording, see: Sprague's Technical Library.
A number of organizations have compiled databases covering thousands of common problems with VCRs, TVs, computer monitors, and other electronics equipment. Most charge for their information but a few, accessible via the Internet, are either free or have a very minimal monthly or per-case fee. In other cases, a limited but still useful subset of the for-fee database is freely available. A tech-tips database is a collection of problems and solutions accumulated by the organization providing the information or other sources based on actual repair experiences and case histories. Since the identical failures often occur at some point in a large percentage of a given model or product line, checking out a tech-tips database may quickly identify your problem and solution. In that case, you can greatly simplify your troubleshooting or at least confirm a diagnosis before ordering parts. My only reservation with respect to tech-tips databases in general - this has nothing to do with any one in particular - is that symptoms can sometimes be deceiving and a solution that works in one instance may not apply to your specific problem. Therefore, an understanding of the hows and whys of the equipment along with some good old fashioned testing is highly desirable to minimize the risk of replacing parts that turn out not to be bad. The other disadvantage - at least from one point of view - is that you do not learn much by just following a procedure developed by others. There is no explanation of how the original diagnosis was determined or what may have caused the failure in the first place. Nor is there likely to be any list of other components that may have been affected by overstress and may fail in the future. Replacing Q701 and C725 may get your equipment going again but this will not help you to repair a different model in the future. Having said that, here are two tech-tips sites for computer monitors, TVs, and VCRs: * http://www.anatekcorp.com/techforum.htm (currently free). * http://www.repairworld.com/ ($8/month). * http://ramiga.rnet.cgl.com/electronics/info.html (free large text files). These types of sites seem to come and go so it is worth checking them out from time-to-time even if you don't have a pressing need. If possible, download and archive any useful information for use on a rainy day in the future.
Proper care of a VCR does not require much. Following the recommendations below will assure long life and minimize repairs. * Allow adequate ventilation - VCRs are not huge users of power but there is some heat buildup nonetheless. Leave at least 1-1.5 inches around all sides and top for air circulation. Try not to place the VCR near heat producing equipment. * Do not put anything on top of the VCR that might block the ventilation grill. To be safe, don't put anything on top - period. Tapes are especially bad - for the tapes - as the heat and possible magnetic fields in the vicinity will tend to age them prematurely. In addition, modern VCRs are NOT built like the Brooklyn Bridge! The weight of a TV or stereo components could affect the VCR mechanically, messing up tape path alignment or worse. * If possible, locate the VCR away from the TV. Some VCRs are particularly sensitive to interference from the TV's circuitry and while this won't usually damage anything, it may make for less than optimal performance. * Don't locate VCRs in dusty areas if possible. Consider the use of a dust cover when not actually being used if you have no choice of location. * Don't locate VCRs in areas of high (tobacco) smoke or cooking grease vapors. I cannot force you to quit smoking, but it is amazing how much disgusting difficult to remove brown grime is deposited on sensitive electronic equipment in short order from this habit. * Make sure all input-output video and audio connections are tight and secure to minimize intermittent or noisy pictures and sound. * Finally, store video cassettes well away from all electronic equipment including and especially loudspeakers. Heat and magnetic fields will rapidly turn your priceless video collection into so much trash. It is also recommended that you store the cassettes on edge so that the tape edges are not subject to pressing against the case and that you run them through a VCR or winder/rewinder from start to end and back on FF/REW at least once a year (another pair of recommendations that are rarely followed).
"What are the 'good' and 'bad' brands of videotapes (T-120)? Are the 'extra' or "high" grades really better?" I would avoid brands you never heard of. K-mart brand, Recoton(sp), the street vendor from whom you buy Chinese food, whatever. Higher grade tapes are not necessarily worth the expense but in my experience with some like Maxell and Scotch, going one level up from the cheapest is worthwhile and results in a noticeably better picture. Only a few companies actually manufacture the raw tape stock. For what it's worth (FWIW), I usually use Scotch, under $2 for a T120 - usually in a 3 pack for $5 or $6 with one higher grade cassette. The higher grade tapes may actually be harder on the video heads due to their formulation but this probably doesn't matter for the ordinary user.. You don't need HiFi grade tapes for HiFi - any tape will work. However, higher grade tapes may last longer with higher quality results in demanding situations like 24 hour a say security monitoring. Consumer Reports does a review every so often, check back issues. I believe their conclusions were generally to buy name brands by price. Whether you believe in Consumer Reports or not, checking their ratings at least gives you an additional data point.
(From: Raymond Carlsen (rrcc@u.washington.edu)). I have not seen any "official" guidelines on tape longevity for a long time, since the Beta days. Use of old tapes will not generally ruin video heads but may clog them. Proper manual cleaning restores normal operation. Your mileage really depends on several factors, the most important being the conditions under which it's used. I've seen VCRs that can chew up a tape in one or two passes and make it unusable. High humidity and heat will cause tapes to stick to the head drum and wear prematurely. Shuttling tapes back and forth and leaving them sit in pause (on one spot) can accelerate wear. Under ideal conditions: clean machine in good alignment running a tape from beginning to end without stopping is as good as you're going to get. Alignment tape manufacturers used to indicate expected life as the "number of passes". No significant degradation in 50 passes, but after that, dropouts become obvious. Maximum life is 200 passes. At that point, the tape is starting to break down with oxide particles being shed onto the heads (actually happens with all tapes to some degree) causing head clogging. With tapes of any age, a liquid spill such as soda pop ends the game right there. It can be cleaned, but unless it's your precious home movies, forget it. I would use a tape until the dropouts become annoying. Dropouts are places on the tape where the oxide is missing. You'll see them more at the beginning of a tape where it's mechanically stressed by loading and unloading. A lateral scratch on a tape (caused by buildup of gunk in a VCR) will show up as a 3 or 4 line continuous dropout somewhere on the screen. Look at some heavily used rental tapes and you'll get the idea. So, bottom line: use it until it shows it's age. :)
You no doubt have heard that a VCR should be cleaned and checked periodically. This is basically good advice but few people actually do follow it. I cannot give a specific schedule to follow as many factors influence the amount of wear and tear on your VCR: * If you mostly use new brand-name tapes to make your own recordings, rarely play rental tapes, and have the VCR located in a clean cool relatively dust free and smoke free location, you may be able to go 5 years with no problems. However, a more prudent interval would be 1-2 years between preventive maintenance and rubber replacement after 4-5 years. Obviously, if you time shift every evening or have frequent marathon viewing parties you should probably reduce the PM interval. * If you play rental movies every weekend or older tapes and have chain smokers in the house, every 3 months may not be frequent enough. I would suggest 6 months to 1 year between preventive maintenance and rubber replacement after 3-4 years. If you want some guidelines, see the next section: "Sample VCR preventive maintenance schedule". Realistically, you are not going to do any PM anyway. So, just be aware of the types of symptoms that would be indications of the need for cleaning or other preventive or corrective maintenance - erratic loading, need to convince the VCR to perform certain operations, whirring motors without completing cycle, VCR taking longer to go into or out of a particular mode than you recall, jittery or noisy picture, or wavering or muddy sound. If your inspection reveals deteriorated rubber parts, obviously these should be replaced regardless of their age. Of course, acute symptoms like a tape jam or tape munching episode is a sign of the need for emergency treatment. This still may mean that a thorough cleaning is all that is needed. I generally don't consider cleaning tapes to be of much value for preventive maintenance since they do not run long enough or with enough force to clean the rollers, stationary heads, and guide posts. Also, the dry type, in particular, are abrasive and frequent use may cause premature wear to the expensive video heads. The following are some reasons to inspect and clean a VCR periodically: * This will maintain performance at factory new levels. Dirt, dust, and shed tape oxide all contribute to a reduction in stable tape movement and possible problems with noisy or jumping pictures and muddy or wavering sound. * Dirt, dust, and other crud can be deposited on the tapes you run through the VCR contaminating them and passing problems on to this or other VCRs in the future. * Your inspection will reveal if service parts like belts, tires, the pinch roller, etc. are in good conditions so that future surprises will be minimized. If you follow the instructions in the section: "General guide to VCR cleaning and rubber parts replacement", there is minimal risk to the VCR. However, don't go overboard. If the belts are in good condition (by appearance and stretch test), just clean them or leave them alone. This is especially true in the (generally infrequent) designs of some models of VCR tape transports where significant disassembly is required to replace a belt. In this situation, you risk not being able to put everything back the way it was. Most belts can be replaced with little or no disassembly beyond removing the top and bottom covers and possibly any circuit boards that may be in the way, Sometimes one or two additional screws will need to be loosened or removed to move a bracket or shield.
Here is an example of the recommended inspection, lubrication, and
replacement schedule for a typical VCR as provided by the manufacturer.
This is from the Sams VCRfact for a particular non-HiFi RCA VCR. I am
providing this for information only and am not necessarily recommending
these or other similar hard and fast rules for VCR preventive maintenance.
It is not clear here what a 'tape' is though the comments that go along with
this table seem to indicate that it means a T120. However, parts that deal
with tape loading are affected not by how long a tape is played but by the
number of loading cycles. Wear on the video heads, on the other hand is
strictly a function of play/record time. Wear of the A/C and erase heads
depends on both time and tape speed. Thus, these are additional reasons
not to take the numbers below too literally.
After What to do Which parts
------------------------------------------------------------------------------
250 tapes Clean A/C head, capstan, erase head, pinch roller,
impedance roller, supply reel table, takeup
reel table, video heads.
500 tapes Replace Video heads (upper cylinder).
750 tapes Replace Pinch roller
1000 tapes Grease Loading cam gears, impedance roller shaft,
roller guide tracks.
Oil Supply reel shaft, takeup reel shaft.
Replace Reel belt, loading motor belt, main brake
spring, main brake arms (left and right).
2000 tapes Replace A/C head, erase head, supply reel table,
takeup reel table.
2500 tapes Replace Cylinder unit.
It would be nice for your VCR if rental movies had never been invented. You have no idea of the history of any tape you bring home. The following may also apply to tapes in your video library or tapes given to you by friends or relatives: * The tape may be old and old tapes shed a lot more oxide and crud than newer tapes. A single playing may clog your video heads. * The tape may have been damaged by a prior viewing and one pass through may ruin your expensive video heads. A tape that has been seriously crinkled due to a VCR tape eating incident and then wound back into the cassette may be a ticking time bomb for your VCR. A tape with a partial break or one that has been improperly spliced is even more likely to cause serious damage. Do not splice tapes - see the section: "Recovering damaged or broken tapes". * The cassette mechanism itself may have been damaged (from being dropped or stored in a hot automobile) with unknown consequences for your VCR. Note: if you should ever damage a rental tape as a result of a cranky VCR or for any other reason, don't just give it back to the video store. Please let them know. Also, if your VCR should jam with a tape inside, do not forcibly extract it - read the appropriate sections later in this document. If in doubt, let the video store know what happened and follow their recommendations. Given that you are not likely to give up the movie couch potato addiction, some problems can be avoided by fast forwarding a couple of minutes into the tape before hitting PLAY. Damage to rental tapes often occurs near the start - and this will avoid some of the useless coming attractions as well! If you notice the video breaking up or deteriorating while you are watching, immediately ejecting the tape may be the most prudent option since the worst may be yet to come! While I cannot control your viewing habits, playing a lot of old, dirty, deteriorated tapes (rental or from your own tape library) will eventually take a toll on your VCR. At the very least, you should perform a general cleaning and inspection at more frequent intervals. (From: Jim Lagerkvist (jlager@tir.com)). Renting a video tape has all the same potential consequences as renting a hooker. That tape may pass to your machine anything from pizza grease to splices made from duct tape or staples. I keep two VCRs in my house. One for rental tapes and another for known trusted tapes.
Once you remove the cover(s) of a VCR (ignoring the warnings about no user serviceable parts, etc.), there are some risks to you and your VCR. You also, of course, void the warranty (at least in principle). Therefore, if the unit is still under warranty, having it serviced professionally may be your wisest option. Stay away from the line side of the power supply - put electrical tape over the exposed connections. To be doubly sure, tape a piece of cardboard or thick plastic over the power supply section. Other than that, there is more danger of damaging the VCR by accidentally shorting something out or breaking a little plastic doodad than of you getting hurt. * Don't wear any jewelry or other articles that could accidentally contact circuitry and conduct current, or get caught in moving parts (protect long hair as well). * If circuit boards need to be removed from their mountings, put insulating material between the boards and anything they may short to. Hold them in place with string or electrical tape. Prop them up with insulation sticks - plastic or wood. * Connect/disconnect any test leads with the equipment unpowered and unplugged. Use clip leads or solder temporary wires to reach cramped locations or difficult to access locations. * If you must probe live, put electrical tape over all but the last 1/16" of the test probes to avoid the possibility of an accidental short which could cause damage to various components. Clip the reference end of the meter or scope to the appropriate ground return. * Perform as many tests as possible with power off and the equipment unplugged. For example, the semiconductors in the switching power supply of a VCR can be tested for shorts and the fusable resistors can be tested for opens. * If you need to probe, solder, or otherwise touch circuits in a switching power supply with the power off, discharge (across) large power supply filter capacitors with a 2 W or greater 20-100K resistor and then verify with your voltmeter. * The use of GFCI (Ground Fault Circuit Interrupter) protected outlet is a good idea but will not protect you from shock from many points in a line connected power supply. A circuit breaker is too slow and insensitive to provide any protection for you or in many cases, your equipment. A GFCI may prevent your scope probe ground from melting should you accidentally connect it to a live circuit, however. * Don't attempt repair work when you are tired. Not only will you be more careless, but your primary diagnostic tool - deductive reasoning - will not be operating at full capacity. * Finally, never assume anything without checking it out for yourself! Don't take shortcuts!
Many problems have simple solutions. Don't immediately assume that your problem is some combination of esoteric complex convoluted failures. For a VCR, it may just be a bad belt or an experiment in rock placement by your 3-year old. Try to remember that the problems with the most catastrophic impact on operation (a VCR that eats tapes) usually have the simplest solutions (replace the idler tire). The kind of problems we would like to avoid at all costs are the ones that are intermittent or difficult to reproduce: the occasional interference or a VCR that sometimes will not record your favorite soaps on alternate Thursdays before a full moon. If you get stuck, sleep on it. Sometimes, just letting the problem bounce around in your head will lead to a different more successful approach or solution. Don't work when you are really tired - it is both dangerous and mostly non-productive (or possibly destructive). Whenever working on precision equipment, make copious notes and diagrams. You will be eternally grateful when the time comes to reassemble the unit. Most connectors are keyed against incorrect insertion or interchange of cables, but not always. Apparently identical screws may be of differing lengths or have slightly different thread types. Little parts may fit in more than one place or orientation. Etc. Etc. Pill bottles, film canisters, and plastic ice cube trays come in handy for sorting and storing screws and other small parts after disassembly. Select a work area which is well lighted and where dropped parts can be located - not on a deep pile shag rug. Something like a large plastic tray with a slight lip may come in handy as it prevents small parts from rolling off of the work table. The best location will also be relatively dust free and allow you to suspend your troubleshooting to eat or sleep or think without having to pile everything into a cardboard box for storage. Another consideration is ESD - Electro-Static Discharge. The electronic components in a VCR are vulnerable to ESD. There is no need to go overboard but taking reasonable precautions such as getting into the habit of touching the chassis first before any of the electronic components is a good practice. The use of an antistatic wrist strap would be further insurance. A basic set of precision hand tools will be all you need to disassemble a VCR and perform most adjustments. These do not need to be really expensive but poor quality tools are worse than useless and can cause damage. Needed tools include a selection of Philips and straight blade screwdrivers, needlenose pliers, wire cutters, tweezers, and dental picks. A jeweler's screwdriver set is a must particularly if you are working on a portable VCR or camcorder. For adjustments, a miniature (1/16" blade) screwdriver with a non-metallic tip is desirable both to prevent the presence of metal from altering the electrical properties of the circuit and to minimize the possibility of shorting something from accidental contact with the circuitry. You should not need any VCR specific tools with the possible exception of a miniature metric hex key wrench set for loosening the set screws on the roller guides should you need to perform a tape path alignment. I have never needed a VCR head puller. You can make a tool for the special nut found on many A/C head assemblies for tracking adjustment by filing a slot in the blade of a straight blade screwdriver. A low power fine tip soldering iron and fine rosin core solder will be needed if you should need to disconnect any soldered wires (on purpose or by accident) or replace soldered components. See the document: "Troubleshooting and Repair of Consumer Electronics Equipment" for additional info on soldering and rework techniques. For thermal or warmup problems, a can of 'cold spray' or 'circuit chiller' (they are the same) and a heat gun or blow dryer come in handy to identify components whose characteristics may be drifting with temperature. Using the extension tube of the spray can or making a cardboard nozzle for the heat gun can provide very precise control of which components you are affecting. For info on useful chemicals, adhesives, and lubricants, see "Repair Briefs, an Introduction" as well as other documents available at this site. If you have several VCRs or do repairs for friends (former friends?), there are inexpensive kits of VCR mechanical parts like washers and springs that come in handy. General belt or similar kits are not worthwhile unless you are in the service business - there is too much variety in the sizes and other characteristics of these types of parts to make an assortment a good investment. Note: while working with the top off, you may need to put pieces of strategically located cardboard over the area of the cassette to block extraneous light from causing erratic behavior (modes aborting, not starting at all, etc.) with the start/end-of-tape sensors. Not all VCRs are sensitive to extraneous illumination but I have been bitten more than once by not doing this. Using overhead instead of direct illumination will probably help as well. In extreme cases, placing electrical tape over the end sensors may be needed but this will likely confuse the microcontroller under certain conditions into thinking that a non- existent tape is present - or if your troubleshooting will permit, leave a cassette in the transport. (I have heard of at least one case where this was a problem even for normal operation - apparently, light was falling on the VCR in just the wrong way where it happened to be located. The VCR would enter rewind mode regardless of what the helpless human wanted unless tipped on end!)
Don't start with the electronic test equipment, start with some analytical thinking. Many problems associated with consumer electronic equipment do not require a schematic (though one may be useful). The majority of problems with VCRs are mechanical and can be dealt with using nothing more than a good set of precision hand tools; some alcohol, degreaser, contact cleaner, light oil and grease; and your powers of observation (and a little experience). Your built in senses and that stuff between your ears represents the most important test equipment you have. A DMM or VOM is necessary for checking of power supply voltages and testing of sensors, LEDs, switches, and other small components. Unless you get deep into the electronic repair of VCRs, an oscilloscope is not required. There are two items of important test equipment that you probably already have: * A video signal source - both RF and baseband (RCA jacks). Unless you are troubleshooting tuner or video/audio input problems, either one will suffice. RF sources include a pair of rabbit ears or an outdoor antenna, a cable connection, or a VCR with a working RF modulator. Similarly, a working VCR makes a handy baseband or RF signal source. * A display device. A video monitor or TV makes an excellent video signal display. Many video problems can be diagnosed by just examining the picture. If you have an old TV with a vertical hold control, this is useful when adjusting backtension, should the need arise. A B/W TV is adequate for many of the tests you will be performing.
If you have no prior experience with precision electromechanical repair, don't just jump in as the following actual experience demonstrates: (From: someone who would prefer not to be identified). "Ok, I did something dumb. I was given an old VCR (early 80s) a couple weeks ago (JVC-7100U). It stopped playing and recording, but FF and rewind worked fine. Reading the FAQ, I decided to check it out. I took the top off, and was trying to make the motor run so I could see the problem. There was an incandescent light, and I figured there was a light sensor, so I moved the lamp out of the way. The FAQ suggests electrical tape over the lamp, but I hadn't read it yet. My manipulation caused the lamp to fail. Until I could replace it, I just jumped the connection, which worked fine for awhile. I had just figured out the problem with play/record was a drive wheel not making contact with the take-up reel. It seemed to be a result of a weak spring, and I was trying to figure out which one, when the screwdriver I was manipulating the arm with slipped, and contacted the back side of a circuit board. Lesson number two: Use a chopstick for that purpose. I believe it was at this point I realized I got no reaction from any of the VCR control buttons, so maybe I shorted something out. All the buttons worked before. Even worse, as I was reinstalling the tape loading mechanism, the screwdriver slipped again, in a different place, and I did see a flash when it contacted the back of the circuit board. Whoops." Don't let this happen to you. Or, at least start out with an old expendable VCR and accept the hits to your pride!
When troubleshooting mechanical problems in a VCR, one of the handiest accessories is a cassette cheater - a frame to fool the VCR into thinking there is a cassette in place so that you have access to the reel spindles and idler. You can buy these for $6-12 but you can make one that is almost as nice: * Take a discarded cassette, open it up and throw away everything but the top and bottom halves and the screws. * Punch out the plastic windows - and somewhat more of the top and bottom if you are so inclined - relatively little of the original structure is actually needed to fool the microbrain of the VCR! The more open the cheater is, the easier it will be to see and access guts of the VCR while running. * Reassemble the two halves of the cassette with the screws (you did save the screws, right?). * Put a bit of black tape over the sensor holes on the sides of the cassette (near where the hinge pins of the flap went). These cheaters will load and 'play' just fine except that some machines actually sense that the supply reel is being turned by the tape movement during loading or always and will shut down if it isn't (among other peculiarities) so you may have to do this by hand. There are several benefits to using one of these, one of which is that there is no chance of ruining a prized tape due to a hungry VCR. You will also be able to feel the spindles to get an idea whether they are turning properly and with enough torque in all modes. If you break out enough of the top and bottom, you will have access to the idler and other under-cassette parts at the same time. If you examine one of the commercial cassette cheaters, you will see that very little is needed beyond the outer frame as long as it sits properly on the indexing posts and doesn't jam the mechanism when loading/ejecting.
When aligning the tape path, a test tape will be needed as a reference. Actually, you want two - one recorded at the SP (2 hour) speed and another recorded at the EP (6 hour) speed. These do not need to be exorbitantly priced professional alignment tapes. A couple of recordings made on a known working VCR will get you close enough for most purposes. Do not use these same tapes for diagnosing or testing of mechanical problems, your VCR may be hungry and they may get eaten. For general video diagnosis including mechanical and tape eating problems, a bunch of sacrificial tapes is handy - advertising, promos, feature shorts - anything you do not care about but have been recorded on working VCRs. Very often they get mangled and you do not want to continue to use mangled tapes which may damage the VCR - in particular the video heads. However, once you have the VCR basically working, you will want to test it start to finish on a T120 cassette. This is because the reel hub size on those short video cassettes is not the same as a standard (most commonly used) T120 cassette and may mask problems if the VCR is mechanically marginal in some respects.
You will void the warranty - at least in principle. There are usually no warranty seals on a VCR so unless you cause visible damage or mangle the screws, it is unlikely that this would be detected. You need to decide. A VCR still under warranty should probably be returned for warranty service for any covered problems except those with the most obvious and easy solutions. It is usually very easy to remove the top and bottom covers on VCRs. For the top cover, there are usually some very obvious screws on the back or sides, and in rare cases on the top. There may be a couple of screws on the bottom as well that secure the top cover. For top loaders, you will probably need to remove the cassette holder lid - there will be two screws, perhaps hidden by rubber plugs. Once all the screws are out, the top cover will lift up or slide back and then come off easily. If it still does not want to budge, recheck for screws you may have missed. For the bottom cover, there are usually a half dozen or so screws around its perimeter and sometimes in the middle as well. There may be one or two grounding screws as well which are of different length and threads - these should go back in the same location from where they came. Bottom covers are usually simple sheet metal. In rare cases, you will need to remove the front panel to free the bottom cover (or vice-versa). Circuit boards may prevent access to the top or bottom of the tape transport. Usually, removal of a few screws (often marked with red paint or arrows on the circuit board) and perhaps pressing of a couple of snaps will permit the board to be swung up on a hinge out of the way. Front panels usually snap off, possibly requiring the removal of a few screws on top or bottom. Make notes of screw location and type and store the screws away in a pill bottle, film canister, or ice cube tray. When reassembling the equipment make sure to route cables and other wiring such that they will not get pinched or snagged and possibly broken or have their insulation nicked or pierced and that they will not get caught in moving parts. Replace any cable ties that were cut or removed during disassembly and add additional ones of your own if needed. Some electrical tape may sometimes come in handy to provide insulation insurance as well.
There are various sensors in a VCR that are light sensitive - it is not a safety interlock (though it acts this way in some VCRs) but a result of the way the tape start and end sensors operate. VHS tapes have a clear leader and trailer. An LED or light bulb poking up near the center of the cassette shine towards sensors at either side of the cassette. When light is detected the VCR assumes that it is at the appropriate end of the tape and shuts off (or rewinds if in PLAY mode when it senses the end depending on model). During servicing, a piece of opaque cardboard or other insulating material should be placed above the cassette basket if any strange behavior is detected that was not present with the cover in place. Not all VCRs are particularly sensitive external illumination.
This should be the first step in any inspection and cleaning procedure. Do not be tempted to use compressed air! I would quicker use a soft brush to carefully dust off the circuit boards and power supply. Work in such a way that the resulting dust does not fall on the mechanical parts. For the deck itself, using compressed air could dislodge dirt and dust which may then settle on lubricated parts contaminating them. High pressure air could move oil or grease from where it is to where it should not be. If you are talking about a shop air line, the pressure may be much much too high and there may be contaminants as well. A Q-tip (cotton swab) moistened with politically correct alcohol can be used to remove dust and dirt from various surfaces of the deck (in addition to the normal proper cleaning procedures for the guides, rollers, heads, wheels, belts, etc.)
We have all done this: a tiny washer or spring pops off and disappears from sight inside the guts of the unit. Don't panic. First - unplug the VCR if it is plugged into the AC. Remove the battery pack from a camcorder. Try to locate the part with a bright light without moving the VCR. You may have gotten lucky (yeah, right). Next, over an area where a dropped part will be visible (not a shag carpet!), try any reasonable means to shake it loose - upside down, a little gently tapping and shaking, etc. A hard surface is better in some ways as you might hear the part drop. On the other hand it may bounce into the great beyond. If this does not work, you have two options: 1. Assume that the part has landed in a place that will not cause future problems. There could be electrical problems if it is metallic and shorts out some circuitry or there could be mechanical problems if it jams some part of the mechanism. There is an excellent chance that the part will never cause any harm. What chance? I don't know, maybe 99%. It is not worth taking the unit to pieces to locate the part. You are more likely to damage something else in the process. Obtain a replacement and get on with your life. The exception is, of course, if you now begin experiencing problems you **know** were not there before. 2. Take the unit to pieces in an attempt to locate the part. For all you know, it may be clear across the room and you will never find it inside. If all the gymnastics have not knocked it loose, then it may be really wedged somewhere and will stay there - forever. If the VCR behaves normally, then in all likelihood it will continue to do so. To prevent this sort of thing from happening in the future you will no doubt be much more careful. Sure you will! Some suggestions to prevent ejection of an E-clip, split washer, or spring into the great beyond: * Construct a paper dam around the area. * Tie a thread or fine wire around the part before attempting to remove it. Keep this 'safety line' on until after it has been reinstalled, then just pull it free. * Keep one finger on the part as you attempt to pop it free. * Hold onto the part with a pair of needlenose pliers or tweezers while prying with a small screwdriver.
Thanks to Brian Siler (bsiler@PROMUS.com) for using his Snappy(tm) rig to capture the original photos. Please refer to the photo: Typical VHS VCR Tape Transport Components for parts identification. The following description applies to 99.9% of the VCRs in existence today. I have seen one that had a sideways loading mechanism - very weird. Looking at the unit from above with the front toward you: * Supply spindle - left hand side platform on which the supply tape reel (inside the cassette) sits. The edge which contacts the idler tire, and associated brake pad, should be cleaned. * Takeup spindle - right hand side platform on which the takeup tape reel (inside the cassette) sits. The edge which contacts the idler tire, and associated brake pad, should be cleaned. * Idler - assembly which swings between supply and takeup reels and transfers power to the appropriate reel to wind the tape up during play and record and often to drive FF and REW. This may use a rubber tire or a gear. * Idler tire - the black rubber ring on the outside of one part of the idler which actually contacts the reel edges. This is single most likely part to need replacement after a few years of use. Some VCRs use a gear instead of a tire, but the tire is most common, especially in older units. Clean and inspect - replace if in doubt. See VCR with Idler Tire for a typical tire-type idler assembly. Some VCRs use gears in place of rubber (as is the case with the VCR shown in the photo: Typical VHS VCR Tape Transport Components. Teeth can break off but these are generally quite reliable. Some high-end decks may have separate motors for reel rotation. * Roller guides - there are two, one on each side. These assemblies move from their retracted position toward front of machine to their loaded position for play and record. The white rollers should spin freely and be clean. When retracted, the roller guide assemblies will be slightly loose. However, when the tape is wound around the video head drum, they must be snug against the V-Stoppers - the brackets at the end of the tracks. Also on the same assembly are tilted metal guide posts - again one for each side. These sometimes fall out with obvious consequences. Proper functioning and adjustment of the roller guides is the most critical requirement for proper tracking. (However, do not touch their settings without being really sure that they are at fault and not until you have read the sections relating to tape path alignment.) Clean and inspect. * Roller guide tracks - combination of plastic and metal slots in which the roller guide assemblies slide during tape loading and unloading. Check to make sure there is still some healthy grease on the surfaces. If gummed up or excessively dirty, clean and relube with a dab of plastic-safe grease on each sliding surface. * Video head drum or upper cylinder - approximately 2.45 inches in diameter by .75 inches high. This rotating assembly contains the video heads (and HiFi audio and flying erase heads, if present). Stay away from this unit. as video heads are very delicate. If you must clean it, refer to the specific instructions on cleaning video heads elsewhere in this document. Video heads do not normally require cleaning despite what the cleaning tape people will have you believe. If you are not having video noise problems, they should be left alone. * Capstan - right side after tape exits from roller guide. The capstan is a shaft about 3/16" diameter which during play and record (and search) modes control tape movement forward or reverse when the pinch roller is pressed against it. Should be cleaned thoroughly to assure proper tape movement during play, record, and search modes. * Pinch roller - black rubber roller about 1/2" diameter, 3/4" high which spins freely and is pressed against the capstan during play, record, and search modes. It is constructed as a molded rubber sleeve fused to a metal roller on a small ball bearing. A hard, shiny, dried out pinch roller can lead to tape edge munching and erratic sound, speed, and tracking. Clean thoroughly. Inspect for cracked, hard, shiny, or otherwise deteriorated rubber and free and smooth rotation. Even if you have no obvious record or playback symptoms, if the pinch roller appears concave or with a distinct worn ridge, replacement is recommended - erratic behavior will soon be the result. A tape which runs off center due to a bad pinch roller may result in tape edge damage and over time can also alter the wear pattern of the audio/control head and various guide posts. * Audio/control Head Stack - between right roller guide (when tape is loaded around drum) and capstan. Includes magnetic heads for non-HiFi (linear) audio and synchronization control track. Should be cleaned since tracking and non-HiFi audio performance is critically dependent on its performance. * Back tension arm - left side just as tape exits cassette - this is coupled to a felt Back Tension Band and serves to maintain a constant tension on the tape during play, record, and forward search. Retracts toward cassette when tape is unloaded. Back tension is somewhat critical and may need adjustment after long use. * Various other fixed guide posts - vertical stationary metal posts which tape contacts. Should be cleaned but rarely need adjustment. The positions of these vary somewhat by manufacturer. * Full erase head - left side towards rear which tape passes over just before going around roller guide, guide post, and drum. Rarely causes problems. Clean. * Impedance roller - left side near full erase head. Freely rotating roller stabilizes tape movement. Some VCRs lack this component. Clean. * Half loading arm - right side near capstan/pinch roller. On VCRs with 'rapid or instant access transports' this helps to position the tape in the intermediate (half loaded) position. A similar arm is usually present in other VCRs and helps to position the tape around the pinch roller. Check for free movement. Clean. Lubricate bearing if sluggish. * Belts - various size black rubber bands - a typical VCR will have between 0 and 12 of these on top and bottom. Typical is 3 or 4. Most are of square cross section though an occasional belt may be flat or round. The belts will need replacement after a few years. Clean and inspect. Replace any belts that are hard, cracked, stretched, or flabby. A good belt will feel soft and rubbery without cracks or other signs of deterioration. It will return to its relaxed length instantly if stretched by hand about 25%. Belt kits are generally available by VCR model but individual belts can be ordered as well. In either case, this is very low cost maintenance which can make an absolutely huge difference in the happiness of your VCR. New belts can often restore a comatose VCR to perfect health. For additional information on replacement rubber parts, see the section: "Determining belt, tire, and pinch roller specifications".
(From Alex (ramjam@globalserve.net)): 1. To confirm that a worn idler tire is causing a malfunction, without disassembly, I use a product called "Rubber Renue" (M.G.Chemicals Ltd. 13-80 Hale Road, Brampton, ON L6W 3M1 Canada 416 454-4178). First I clean the tire with isopropyl alcohol (99%) then using the other end of the Q-tip I apply Rubber Renue. You don't need much, I have had the same 100 ml (3.4 oz.) bottle for over 6 years. What the product does is rejuvenates and conditions the rubber (read: makes *sticky*) as to allow normal or near normal operation. I don't recommend this as a permanent fix, though it can be, it is a great diagnostic tool and the whole procedure takes about five minutes. 2. To fix squeaky pulley shafts and collars I use a pipe cleaner (most smoke shops sell them) to clean the collars, I then use transmission fluid (the same stuff you put in your car) as a lubricant on the shaft. It's lightweight, it doesn't gum up, it's cheap and can be bought just about anywhere. Just remember not to use too much as it spreads easily, which can be disastrous in a VCR.
* VCR refuses to FF or REW and shuts off. * VCR shuts off entering PLAY or REC or at random during PLAY or REC. * VCR eats tapes. * VCR doesn't accept tapes or ejects them without cause. * Sound is wavery, fluctuating, or muddy. The cause for all of these is very often a bad idler tire or other dirty, worn, or tired rubber parts. See the section below: "General guide to VCR cleaning and rubber parts replacement". A VCR that just munched down your favorite tape is very likely only in need of a little tender loving care. WARNING: Don't turn a simple repair into a full length double feature. Most tires and belts come off without extensive disassembly. However, if your VCR is the exception, DO NOT remove anything to get at the rubber part that may be part of a critical timing relationship - racks or gears, for example - before fully understanding the implications of this action. In some cases, if a gear is rotated even one tooth from where it should be, there can be unforeseen and catastrophic consequences. See the section: "Mechanical relationships in VCRs" for more information before proceeding any further!
All the guideposts, wheels, and rubber parts of a VCR should be cleaned periodically - how often depends on usage. Of course, no one really does it unless something goes wrong. Do not attempt to clean the video heads until you follow the proper procedure given elsewhere in this document, you can break them - very expensive lesson. In most cases, they do not need attention anyhow. Q-tips and alcohol (91% medicinal is ok, pure isopropyl is better. Avoid rubbing alcohol especially if it contains any additives) can be used everywhere except the video heads. Just dry quickly to avoid leaving residue behind or damaging the rubber parts further. Cleaning may get your machine going well enough to get by until any replacement rubber parts arrive and to confirm your diagnosis. Things to clean: 1. Capstan and pinch roller. These collect a lot of crud mostly oxide which flakes off of (old rental) tapes. Use as many Q-tips (wet but not dripping with alcohol) as necessary to remove all foreign matter from the capstan (the shiny shaft that pulls the tape through the VCR for play and record). Just don't get impatient and use something sharp - the crud will come off with the Q-tips and maybe some help from a fingernail. Clean the pinch roller (presses against the capstan in Play, Record, and Search mode CUE and REVIEW) and until no more black stuff comes off. Use as many Q-tips as necessary until no more black gunk collects on Q-tip. If the pinch roller is still hard, shiny or cracked, it will probably need replacement. Many are available for about $6 from the sources listed at the end of this document. It is sometimes possible to put the pinch roller in an electric drill, drill press, or lathe, and carefully file off the hard shiny dried out rubber surface layer, but only use a last resort - and this fix is probably temporary at best. 2. Various guideposts including the roller guides (the white rollers on metal posts which are near the video head drum when in play or record mode). When in FF or REW, or with no tape present, these move on tracks to a position toward the front of the VCR. Note that the roller guides with the white rollers and tilted metal posts will be fairly loose when in the unloaded position (but you should not be able to lift them off the tracks). When actually playing or recording a tape, they will be snug against the stoppers at the end of the tracks. 3. Idler tire (idler swings between reels and transfers motor power to reels - clean until no more black stuff comes off. A dirty or worn idler tire is probably the single most common VCR problem. If the idler tire appears cracked, glazed, or dried out, it will need to be replaced. About $.50-$1.00. As a temporary measure, you can usually turn the tire inside-out and replace it. The protected inner (now outer) surface will grip well enough to restore functionality until a replacement tire arrives - and verify the diagnosis as to the cause of your problem. Also, the idler assembly includes a slip clutch. If this weakens, the idler may not have enough force to press on the reel table edges. If it becomes too tight, there may be audio, video, or crickled tape problems and/or excess wear of the idler tire. When in doubt, the entire idler assembly is often available as a replacement part. They can often be disassembled and adjusted if necessary. 4. Reel table edges - surface on the reel tables where the idler contacts. 5. Audio/control head (right side) and full erase head, (left side). Q-tips and alcohol are ok for these. 6. Anything else that the tape contacts on its exciting journey through your machine. 7. Rubber belts. Access to some of these will probably require the removal of the bottom cover. After noting where each belt goes, remove them individually (if possible) and clean with alcohol and Q-tips or lint free cloth. Dry quickly to avoid degrading the rubber from contact with the alcohol. If a belt is trapped by some assembly and not easy to remove, use the Q-tip on the belt and/or pulley in place. However, if it is stretched, flabby, or damaged, you will need to figure out how to free it. Make sure that there are no twists when a square cut belt or replacement is installed on its pulleys. On some models, you may need to unscrew circuit board(s) blocking access to either the top or bottom of the tape transport. Make notes of what went where - particularly different types of screws and routing of wires. Any belts that appear loose, flabby or do not return instantly to their relaxed size when stretched by 25% or so will need to be replaced and may be the cause of your problems. Belts cost about $.30-$2.00 and complete replacement belt kits are often available by model for $3.-$12. Meanwhile, the belts will function better once they are cleaned, maybe just enough to get by until your replacements arrive. 8. Video heads: READ CAREFULLY. Improper cleaning can ruin the expensive video heads. DO NOT attempt to clean the video heads without reading and following the procedure described in the section: "Video head cleaning technique". While VCRs should be cleaned periodically, the video heads themselves usually do not need cleaning unless you have been playing old or defective rental tapes which may leave oxide deposits on the tips of the delicate ferrite head chips. Unless you are experiencing video snow, intermittent color, or loss of or intermittent HiFi sound (HiFi VCRs only, the HiFi heads are located on the video head drum and for the purposes of cleaning, treated the same way) leave the video heads alone. If you really feel that video head cleaning is needed, refer to the sections on video head problem diagnosis and cleaning elsewhere in this document.
(From: Gillraker (eternity@mcp.cybertron.com)). I pride myself on the cleanings I do with all repairs, I like to keep my shop up to command performance and a cut above the rest I usually even clean up the chassis and deck of most equipment and relubricate and all the trim. I have seen my share of broken heads come in from people after they use a Q-tip...or a store bought cleaning tape... I use a few different size hemostats with a folded up lint free cloth. When folded, it really buffs the cylinder units and leaves a nice shine on the tape guide rollers, and audio and erase heads too. I have cleaned a head with chamois swabs and then gone over them with my own cloth and was horrified to see the residue that was left from ordinary swabs, when it was all collected on the cloth. It doesn't snag the video or stereo hi-fi heads either - I have cleaned a few thousand this way and never snagged any. I use generation 2000 disk cleaner for heads and acetone to degrease the posts and capstan - just a dip - not too much. (Editor's note: take care with strong solvents like acetone - both to protect your health and avoid damage to plastic parts. --- sam)
(From: Thomas L DeTogne (tdetogne@home.com)). Pardon me while I trip over my long gray beard :-). In the old days, we used to clean the platters in a disk drive using what were essentially tongue depressors wrapped with a Texwipe (Lint-free paper). We would first use 99% pure isopropyl alcohol and follow it with freon. (AAAAAh! the Ozone layer!) We would then manually run the heads out over the platters (while they were spinning) and listen for 'ticks'. If we heard any, we'd repeat the process. For those who smoked in the computer room, the residue could build up rather thick and evenly. Getting the whole mess off was a chore. If such was the case, I actually would use Soap and water, followed by water, then the alcohol and finally the freon. (This was more like R-22 and not the R-12 variety. That, we used do dump into the atmosphere freely trying to cool down components.) I have resurrected many road-kill VCRs by using those cleaning techniques on them. I haven't as yet had to use soap, but using other than alcohol proves beneficial. Just don't get too liberal with any of the cleaning fluids. By the way, the freon was used to remove any residue left behind by the alcohol.
The short recommendation is: Don't add any oil or grease unless you are positively sure it is needed. Most parts in a VCR are lubricated at the factory and do not need any further lubrication over their lifetime. Too much lubrication is worse then too little. It is easy to add a drop of oil but difficult and time consuming to restore a VCR that has taken a swim. NEVER, ever, use WD40 in a VCR! WD40 is not a good lubricant despite the claims on the label. Legend has it that the WD stands for Water Displacer - which is one of the functions of WD40 when used to coat tools. WD40 is much too thin to do any good as a general lubricant and will quickly collect dirt and dry up. It is also quite flammable and a pretty good solvent - and there is no telling what will be affected by this: (From: Matthew Fries (freeze@visi.com)). "I heard a horror story when I was in tech school about someone who heard a little squeaking inside the VCR when it was in PLAY mode, so he sprayed WD40 in through the tape door (front loading) and 'lubricated' the entire inside of the VCR. The students who were working on this took apart the entire mechanism, sprayed it clean with TF solvent (4 cans - there goes the ozone) and it still didn't work. No surprise." A light machine oil like electric motor or sewing machine oil should be used for gear or wheel shafts. A plastic safe grease like silicone grease or Molylube is suitable for gear teeth, cams, and the roller guide tracks. Unless the VCR was not properly lubricated at the factory (which is quite possible), the only likely areas needing lubrication are the roller guide tracks - clean and grease. Sometimes you will find a dry capstan, motor, lever, or gear shaft but this is less likely. In general, do not lubricate anything unless you know there is a need. Never 'shotgun' a problem by lubricating everything in sight! You might as well literally use a shotgun on the VCR!
With audio tape decks, demagnetizing is often recommended to improve sound quality and frequency response. There is some debate as to how much benefit there is to this practice but if done properly, there is little risk. Demagnetizing removes the residual magnetic fields that can build up on ferrous parts of the tape heads and various guideposts and other parts in the tape path which may affect frequency response. For the following, do not go near the video head drum, only perform demagnetization of the stationary A/C head, erase head, and guide posts and rollers. In my opinion, the video heads should almost never need to be demagnetized. The ferrite material from which they are constructed is not prone to easily being magnetized like steel. Use a small demagnetizer designed for a tape deck or cassette deck. Do not use anything homemade that might be too powerful or a bulk tape eraser which would certainly be too powerful. Make sure the tip is covered with a soft material to prevent damage to the finely polished surfaces in your VCR. Turn power on to the demagnetizer when a couple of feet away from the VCR. Then, slowly bring it in close and slowly go over all surfaces of anything that the tape contacts or comes close to in the tape transport. The key word here is **slowly**. Move fast, and you will make the magnetic fields stronger. When finished, slowly draw the demagnetizer away to a distance of a couple of feet before turning it off.
Cassette loading places the cassette into proper position on the tape transport. In a front loader, pushing the cassette gently into the slot should cause a motor to take over and suck it in and down to rest on indexing pins. The mechanism that actually holds the cassette is called the cassette basket. Several types of problems are possible: the VCR may ignore you when you push the cassette in or press EJECT, or it may spit it out immediately or cycle back and forth. On a top loader, you do most of the cassette loading manually, so the only likely problem will be if EJECT does not work. If attempting to load a cassette produces no response (though the VCR has power), then there could be a problem with the microswitch that senses the presence of a cassette, the cassette loading motor (if separate from the main motor), a slipping or broken belt, or a faulty driver or other electronic problem. Sometimes this could mean that the microcontroller is confused due to a faulty mode switch or because the mechanism somehow got into a peculiar state. Manual cycling of the cassette loading mechanism might reset it. Gently push a cassette in and turn the appropriate shaft or pulley by hand. First, try this with the VCR unplugged. If nothing happens or you feel resistance, try the other direction. Assuming you find no problems - there is no significant resistance to your turning and the cassette basket cycles from fully ejected to fully seated on the transport baseplate, leave the cassette basket in a partially loaded position and plug the VCR into the AC power and turn it on (this may not be necessary depending on the design of your VCR). It should now reset itself and either load or eject the cassette. If there are still no signs of a response, a power supply, motor, or electronic problem is likely. Note: If this only happens with T160 (8 hour) tapes, it may be a problem with the thinner tape confusing the sensors. Avoiding these tapes is really the best thing to do since they can cause all sorts of problems (especially if they are an off-brand and of inferior quality to begin with). If you hear a motor whirring but nothing happens, this is almost certainly a slipping or broken belt or something blocking the proper movement a mechanical part. If pushing a cassette into the VCR results in it being ejected as though it tasted really bad (there may or may not be hesitation), or if the cassette cycles back and forth without stopping, there could be several possible causes. If it stops part way during loading, does it pause as though the motor is straining or just abort with no warning? If the former, then check carefully for foreign objects, or lack of lubrication. A typical cause is a belt slipping, usually not the idler in this case. Help it out gently and see if that will complete the cycle. Sometimes it is helpful to cycle the mechanism by hand - turning the appropriate shaft or pulley and feeling and watching for any place where it binds. If the basket moves in the wrong way or you feel any significant resistance, try the other direction. Sometimes, the sticky cassette labels partially or totally peal off and clog the works. You may find a toy or rock inside carefully inserted by your 3 year-old! A bit of the cassette shell might have broken off and jammed the mechanism just to confuse you! If the microcontroller were detecting an abnormality, then it would abort instantly but would most likely try to unload the tape before giving up but not in all designs. It is possible that if the expected behavior is not produced by the end/beginning-of-tape sensors during cassette loading, an abort could be initiated. Therefore, these sensors could be suspect. In some cases, the mode switch may be dirty or faulty. A gear may have broken some teeth or slipped a couple of teeth and the timing relationships may be incorrect. There may be a microswitch that is controlled by the cassette basket position and this may be defective or dirty. Similarly, if the cassette seems to be cycling in and out in an apparently infinite loop, there may be an obstruction or the microcontroller is confused by a bad sensor or the basket is out of synchronization with the rest of the mechanism. A squirt of contact cleaner into the microswitch sensor and/or reflowing its bad solder connections may solve this type of problem. Similar comments apply to cases where pressing the EJECT button produces no response. In particular, if the cassette was loaded successfully and you just finished a thoroughly enjoyable movie, the microcontroller may think the mechanism is not safe and is not ejecting to protect your valuable tape from possible damage should it not be fully retracted into the cassette. As with loading, EJECT may result in partial movement and shutdown or reloading the cassette into the down position. All the same causes apply.
It is a common experience - the rental movie is due back at the video store **now** but no matter how you press the EJECT button, yell, scream, hold your breath, or jump up and down, the cassette refuses to be appear. To remedy the underlying problem, see the sections on: "Cassette loading and eject problems" and other for appropriate information. This section only deals with getting the cassette out without damaging either your valuable recording or VCR. Under no circumstances should you force anything - both your tape and your VCR will be history. First, see if the VCR just got into a confused state - pull the plug and patiently wait a minute or two. This may reset the microcontroller and all will be well. These things happen. If this is not successful, you will need to open up the VCR (unplug it first!) and attempt to cycle the mechanisms by hand. Probably both top and bottom covers will need to be removed. The following procedures assume that there are no broken parts, foreign objects, or other damage which might prevent manual cycling of the tape loading and cassette loading mechanism. (Inspect for toys and rocks.) Also note that some VCR designs use solenoids to engage various operations. This will complicate your task (to put it mildly) as locating and activating the proper ones at the appropriate time is, well, a treat. 1. Tape unloading: The first step is to determine if the tape has been unloaded from the video head drum back into the cassette. If the tape is fully retracted into the cassette - there is no tape showing, then go on to step (2). If not, you will need to figure out which shaft or pulley to turn to unload the tape. Trace the linkage or gears that move the roller guides back to their motor - it may be the main capstan motor or a separate small motor used only for this purpose. Rotate this in the direction which moves the roller guides back towards the cassette. It will take many revolutions - be persistent. If you feel any significant resistance or the roller guides move out toward the drum, turn the other way. The tape is fully unloaded when the roller guides are all the way into the cassette and the tape is straight across the cassette's stationary guideposts. If a single motor performs both the tape loading and cassette loading functions, stop turning as soon as you see the cassette start to rise and read the next section before proceeding. If you are not fully successful or if there is still a tape loop outside the cassette even once you have been turning for what seems to be an eternity, you can still try to eject the cassette but will need to be extra careful not to crinkle the tape as the cassette door closes with the tape sticking out. Before proceeding on in this case, try to find a way to turn one of the reels to pull that tape back in as this will make your task a lot easier. There may be an idler that swings between the two reels and this may be accessible from the bottom (the cassette will block it on top). 2. Cassette unloading. Once the tape is fully retracted into the cassette, the cassette can be ejected safely. If a tape loop is still sticking out of the cassette - and you care about the recording - you will need to be especially careful not to crinkle the tape as the cassette door closes. It is usually not possible to get the cassette fully out without its door closing, so the best you can do is to make sure when this happens, the tape is flat across the gap. With care, it should survive. On a top loader, there is usually a solenoid specifically for EJECT or a simple mechanical pushbutton. Once the appropriate lever is pressed, the cassette should pop up - hold the basket with one hand as you do this to prevent any exposed tape loop from being crinkled. On a front loader, locate the cassette loading motor and begin turning it in the appropriate direction - this will be fairly obvious assuming there are no broken gear teeth or other broken parts and that something isn't totally jammed. If this is the main capstan motor, then just continue turning as in (1). Eventually the cassette should raise up and out. If you have a tape loop, be extra careful not to catch it on any guideposts or obstructions as you remove the cassette. Then, wind it back into the cassette by turning one of the reels (you may have to depress the release button on the bottom of the cassette with a pencil - this is the small hole in the center near the label side.) Assuming the tape is not torn and not badly crinkled, it should be fine. If it is severely damaged, refer to the section: "Recovering damaged or broken tapes".
If for some reason, the microcontroller gets confused and refuses to raise the basket and there is no tape in the VCR, first, try pulling the plug for a minute or two. This may reset the error condition. However, since the mechanism is in an illegal state, the microcontroller may refuse to do anything for fear of making things worse. Assuming that the problem is still present, here are two suggestions: * Manually turn the appropriate motor shaft with power off to put the mechanism through the eject cycle. In many VCRs, this is as simple as turning the EJECT motor or possibly the main motor. Be patient and gentle - it will take a while. If there is some underlying problem which caused the basket to be lowered without a cassette in place, than the VCR may return to the illegal state, do nothing, or do something else that is peculiar once power is restored or any button is pressed. * Convince the microcontroller that a tape really is present when there is none. You need to (1) cover the start/end sensor LED poking up in the center of the deck, (2) depress any other microswitches that sense tape present, press EJECT, and (3) possibly turn the non-driven reel by hand a bit while it is attempting to wind the tape loop back into the cassette. Three or four hands are a definite asset. Make sure you get your fingers out before they are caught! Again, an underlying problem may produce unexpected results. For additional info on initialization problems, see the section: "VCR is failing the power-up sequence".
Usually, the owner will admit that the machine is pre-Jurassic and has never been cleaned or serviced. Anyway, rule out the idler tire as well as the idler clutch - if it weakens, then the idler wheel does not press against the appropriate reel with enough force to grip. Is it s top or front loader? If a top loader, you should be able to trick it into playing a nonexistent tape by covering up the end-of-tape light (the one sticking up in the middle) so that it will think there is a tape inserted. (In some models, there might also be a microswitch.) This may permit you to see what is going on. If a front loader, then it is tougher. You need a cassette cheater (see the section: "Cassette cheaters"). Then, with the cheater in place happily fooling the VCR, feel the spindles while the machine is operating. In FF or REW, you may find that they are not being driven or or being driven very weakly. Try to determine if the idler is even being pushed into position or is hung up on something. If there is any chance that it is the idler tire, try turning it inside-out. The relatively protected inner (now outer) surface may grip well enough to confirm the diagnosis. Has it been serviced in the last 15 years? The last 100 years?
In this case, the tape starts to move - possibly at a reasonable speed - but then may shut down - possibly erratic or tape dependent. Make sure the tape is not the problem - try another one. If it starts the operation (as evidenced by whirring sounds and the tape counter changing numbers) but at some point - perhaps near the end of the tape - aborts and shuts down, then a worn idler tire, worn or broken idler clutch, bad belt, or lubrication problem is likely. See the section: "VCR will not fast forward and/or rewind" as well as "Lubrication of a VCR". With instant start transports - where the tape is maintained around the video head drum for all but the fastest rewind, there could be other control problems as well. If the tape starts fast forwarding or rewinding properly (from a visual inspection with the cover off) but the tape counter does not change value and then the unit shuts down, a reel rotation sensor problem is likely. See the section: "Reel rotation sensors". If the operation aborts at the same location on only certain tapes, there could be pinholes in the tape oxide coating allowing light to pass through and confuse the sensors. This happens mostly with T160 or old well worn tapes. If you can locate the problem area, you can try indelible ink on the NON-oxide side of the tape but DO NOT use adhesive tape or glue. Else, discard the tape or live with its behavior.
While these operations are never exactly quiet, when grinding or squeaking
noises are evident, it is time to at least consider the possibilities.
First confirm that the same thing happens with more than one cassette - it
could be defective.
(Portions from: Alan McKinnon (alan.mck@pixie.co.za)) and Oldguyteck
(edward.croteau@the-spa.com)).
You get several types of noisy rewind:
* A high pitched squeak - dirt and/or dried or lost lubrication on reel
spindles, remove both reel tables, clean and lubricate the shafts. On older
machines you often find this as well on idler pulleys.
* Periodic 'eek-eek-eek' type noise, check for an out of round rotating part
rubbing on something. No pat answers here, you have to get your eyes out
and look.
* A grating metal on metal noise that sounds like car brake pads that should
have been changed 5000 miles ago is always the capstan rubbing on its
bearing. The only cure s a new motor. Ignore those that tell you to strip
and clean the bearing. I've tried this trick at least 10 times on different
machines - it won't last. If a capstan motor is worn enough to howl, the
shaft and bearing are way beyond repair.
Miscellaneous causes:
* Cassette not seating properly and/or tape path alignment problems. Press
down on the cassette during REW or FF and see if it shuts up.
* Brake levers not disengaging completely, pads worn, or misadjusted.
* Missing fiber washers (who worked on the VCR last?); worn, broken, or
distorted gears; other lubrication or dirt problems, etc.
* Bad bearings in main motor (usually older VCRs).
The list goes on and on. In the end, the only way to narrow down the problem
will be with your eyes and ears!
Should you buy a tape rewinder to save wear and tear on your VCR? Take it or leave it. I think they are good if your VCR is old and for whatever reason has trouble with FF or REW. However, sluggish FF or REW may be a precursor to tape eating and should be addressed to avoid an impending failure which may ruin a tape. Rubber parts deteriorate by just existing. The surface layer oxidizes and use may actually be good (don't quote me!). I would not bother with a rewinder just to prevent wear and tear on the motors or heads. In many VCRs - particularly older VCRs without real-time tape counters, the tape is totally retracted into the cassette during high speed FF or REW and does not contact the heads at all. In newer VCRs with real-time counters, the tape will contact the control head lightly but wear should not worth worrying about. Wear and tear on the motors is not a serious problem - much less than playing a tape. If the convenience of being able to rewind off-line is important to you, then there may be no harm in using one. However, some rewinders can be hard on video tapes as they usually do not sense the clear leader but stop rewinding when the tape tension increases at the end of the tape. This may eventually damage the tape and/or pull the tape from the takeup reel hub. I have heard of some crinkling the tape edge and actually mangling tapes. (From: Jim Lagerkvist (jlager@tir.com)). There are dozens of fast rewinder units claiming to save wear on your VCR. The earliest ones snapped-off the clear leader from the hubs. The later ones with IR sensors simply made the real problem obvious: Precious recordings are being damaged by a cheap transport screaming the tape at high speed. The tape is either creased or an edge is rippled (usually the control track). I have a long list of heartbroken people that have lost their archives with these things; me included. If a customer complains about a tape suddenly not viewing well, ask if they use one of these things.
If efforts to record (directly or via the timer) are totally ignored or cause the cassette to be ejected, then the record protect tab on the cassette may be broken off or the record protect sense switch in the VCR may be dirty or defective. This switch sits just under the cassette slot (on front loaders). Locate it by referencing the tab position on the loaded cassette. It can easily be tested with an ohmmeter - if you can get to it. To confirm, short out or disconnect (which you will need to do depends on the design of your VCR) the appropriate wires (maybe there is a connector - this could have bad contacts as well) and see if the VCR is more cooperative.
This is a problem with the process called 'tape loading' - pulling the
tape loop out of the cassette and wrapping it around the spinning video drum,
engaging the capstan and pinch roller and reel rotation.
Check all the belts above and below the deck. Belts can appear to
be firm but if they do not return immediately to their relaxed length when
you stretch them 25%, they will need to be replaced.
With the cover off, observe the behavior when you hit play. (You may need
to put a piece of cardboard over the cassette to block external light from
interfering with the start/end tape sensors). Assuming this is a basic VCR
(no instant start features), you should see:
1. The video head drum begins to spin.
2. the roller guides move smoothly on the tracks, wind the tape around
the drum, and stop snuggly pressed against the 'V-Stopper' at the end
of the tracks.
3. The pinch roller moves into position and presses the tape against the
capstan.
4. The tape begins to move and is wound up by the takeup reel.
5. The picture and sound appear on the TV.
With a 'rapid or quick start' (or it may be called something else) transport,
the tape moves to a half-loaded position when the cassette is inserted.
This is at an intermediate position partially pulled out of the cassette
but not wrapped around the drum. On VCRs with a real-time counter and/or
index search capabilities, the tape will be in contact with the control head.
With an 'instant start' transport, the tape will fully load around the
spinning drum when the cassette is inserted but the capstan will not engage and
no tension will be applied to the tape until you press PLAY or REC. (After
about 5 minutes, the drum will stop and it may unload to the half loaded
or unloaded position.)
Note that for VCRs with a real-time counter and/or index search capabilities,
the tape must be in contact with the control head (but not the video heads)
for all relevant modes. These VCRs (which include many modern units)
must therefore pull the tape at least partly out of the cassette.
In all cases, the completion of the sequence results in approximately
the same mechanical configuration during PLAY.
Several likely possibilities when it shuts down:
1. Everything occurs as above, picture and sound appear for a few seconds,
but then the VCR unloads the tape, ejects the cassette, goes into REW
mode, stops, or shuts off. Two common causes:
* The takeup reel does not turn and tape spills into the machine. This is
sensed by the microcontroller which aborts record or play and attempts
to save your valuable cassette. Most likely cause: old/dirty idler
tire. As a test, turn the idler tire inside-out. The fresh surface will
now work well enough to confirm this diagnosis and will continue working
long enough for your replacement idler tire to arrive. See the section:
"General guide to VCR cleaning and rubber parts replacement".
* The takeup reel is turning properly but one of the reel rotation sensors
or its electronics is defective. As a test, check to see if the tape
counter is changing at any time during the loading and abort process.
Non-real-time tape counters usually get their pulses from this same
sensor. (Real-time counters operate off of the A/C head control pulses
and therefore would not be affected by a defective reel sensor). Some
older VCRs used a belt driven counter - the belt may have broken or fallen
off. Most newer VCRs use an optical sensor which may simply be dirty.
See the section: "Reel rotation sensors".
2. The roller guides are getting hung up and not fully loading the tape
either as a result of an obstruction or dried up grease, or a slipping
tape loading belt (often accompanied by an spine tingling squeal).
Parts may have broken or fallen off of the roller guide assemblies
preventing them from fully engaging the 'V-Stoppers'. A similar
fault may prevent the capstan from fully engaging against the tape
and pinch roller. A toy, candy, or a plastic bit of a cassette shell
may be jamming something.
3. The mode switch sensor is dirty or defective and confusing the poor
microcomputer as to the position of the loading mechanism. In this case,
the loading process may stop half way, pause, and then unload as in
(1) or (2), above. Or, it may do almost anything. See the section
on: "Erratic behavior in various modes".
4. Some other condition such as the end-of-tape sensor thinking that
you are at the end of the tape is aborting the tape loading process.
This might be indicated by a sudden reversal and shutdown rather than
a pause (usually accompanied by the sound of a motor whirring) at some
point attempting to complete part of the cycle. For problems with
record in particular, the record protect tab switch may be dirty or
worn resulting in random aborts.
5. Electronic problems like bad grounds or other bad connections are also
possible. Since with some models, (a number of JVC manufactured VCRs,
for example) ground integrity is via screws through the mainboard, should
these loosen, erratic behavior may result. Tighten the screws.
6. A defective microcontroller or other logic could also be at fault but
this is less likely than any of the preceding.
In this case, the VCR starts to play or record but, say, an hour later, shuts down for no good reason - at least not as a result of a command you thought you issued. Make sure the tape is not the problem - try another one. There may be spots on the tape where the oxide has come off resulting in pinhole (or larger) areas which are activating the end-sensors. Confirm that you are using the proper play or record modes - not OTR (One Time Record) or other timed play or record modes which will likely operate in increments of 15 minutes depending on how many times you press the button. In addition, on certain VCRs, if the program timer is enabled with a program setting that has its stop time occur while you are using the VCR - even if the record operation has been aborted by pressing the stop button - the VCR will shut down. If play or record aborts at the same location on only certain tapes, there could be pinholes in the tape oxide coating allowing light to pass through and confuse the sensors. This happens mostly with T160 or old well worn tapes. If you can locate the problem area, you can try indelible ink on the NON-oxide side of the tape but DO NOT use adhesive tape or glue. Else, discard the tape or live with its behavior. Finally, make sure you are not using any 'insert editing' modes which require a previously laid down control track and would abort once blank tape was reached. See the section: "Recording stops at random times on previously used tapes". Once all the obvious problems and cockpit errors have been eliminated, mechanical problem still likely even though the VCR does not abort immediately. A worn idler tire, worn or defective idler clutch, bad belt, or improperly adjusted backtension, are all possibilities. This is particularly likely if the problem is more likely to occur or only happens near the end of tapes as the required takeup reel torque is greater and any of the above mechanical problems will be exacerbated. With instant start transports - where the tape is maintained around the video head drum for all but the fastest rewind, there could be other control problems as well. If the operation starts properly (as indicated by a changing picture on the TV in play or from a visual inspection with the cover off) but the tape counter does not change value and then the unit shuts down, a reel rotation sensor problem is likely. See the section: "Reel rotation sensors". This could still be due to problems similar to those which cause an immediate abort if some components or connections are marginal. Also see the section: "VCR aborts play or record during startup or shortly thereafter".
The most common cause of a VCR eating tapes is a dirty/worn idler tire preventing the takeup reel from turning. See section: "General guide to VCR cleaning and rubber parts replacement". The idler tire transfers motor power to the appropriate reel hub. If dirty, worn, dried out, glazed, cracked, or otherwise deteriorated, it will slip and cause the takeup reel (in play mode) to stop turning at some point. Hopefully, the microcomputer senses this and tries to wind the tape back into the cassette. But, you guessed it, this requires the idler tire so you end up with a mess of tape inside the machine. When you go to eject, you may get the cassette with a tape loop hanging out. If you are careful, you may be able to extract the tape without crinkling it too badly but don't just pull - it will break or be hopeless damaged. You will need to remove the top cover and carefully lift the tape loop out of the machine and wind it back into the cassette. If there is any significant crinkling or a partial break in the tape, discard the cassette. If it is priceless and irreplaceable, see the section: "Recovering damaged or broken tapes". DO NOT try to use it or just return it to the video store without informing them of what happened - it is unfair the next renter as a badly crinkled or partially broken tape can destroy expensive video heads.
(This may also apply to other modes for a VCR with a 'quick start' or 'instant start' transport.) If your VCR aborts playing unexpectedly and shuts down and then, pushing EJECT results in a tape loop hanging out of the cassette when it is removed, this is considered tape eating - refer to the section: "VCR eats tapes". However, if all other functions work normally but ejecting results in a tape loop, this section is for you. Using a garbage cassette, try to observe exactly what is happening during EJECT. Specifically, is the operation terminating early or is there some problem with the appropriate reel not turning or not turning reliably or quickly enough? Is the tape getting hung up on the roller guides or on some other guideposts? As with tape eating, the most common cause is dirty, old, deteriorated rubber parts - particularly the idler tire - preventing the tape from being fully wound back into the cassette. Therefore, the first step is to follow the procedures in the section "General guide to VCR cleaning and rubber parts replacement". If this only started happening after you had the VCR apart for any reason, recheck your work - you may have neglected a connector, have the mode switch slightly out of position, or have gears which are improperly timed. Many VCRs determine that the tape is completely wound back into the cassette by sensing rotation of the non-driven reel indicating that the tape is pulling on it as a result of being tight and pulled by the driven reel. If this sensor is defective, disconnected, the signal is noisy, or the associated electronics are faulty, the operation may be terminating early. As an experiment to confirm this, use a cassette cheater and while the VCR thinks it is winding the tape back into the cassette, turn the non-driven spindle by hand - this should stop the operation instantly. If it stops too quickly - before you turn the spindle, there could be a problem with this sensor. It is also possible for a failure of one of the reel brakes to allow one of the reels to continue spinning even after motor power has been shut off. Alternatively, a sticky brake band may increase the driven reel torque and fool the microcontroller into thinking that the tape slack has been taken up. If the roller guides get hung up on the tracks while being retracted, even for an instant, the tape may become tight around the roller guides, pull on the non-driven reel, and stop the operation before the tape is fully wound back into the cassette. Check for obstructions and for adequate lubrication of the roller guide tracks. If it is a late model Sony, the 'half loading arm' could need lubrication. See the section: "Late model Sony VCR munches tape on eject".
(From: Gary Woods (gwoods@albany.net)). Usually under humid conditions, but not condensation of tape path, tape has excessive amount of drag around the scanner. S-tension is OK, or even a little light, but there is so much drag around scanner that the capstan skids. * Reducing S-tension helps. * Cleaning scanner helps. * Cleaning capstan and treating pinch roller with PRB "conditioner" (smells like ether) helps. None of these is a *real fix* and the problem recurs eventually. Somewhat dependent on the tape, but real problem appears to be drag around lower drum. Anyone know of a fix other than a new scanner? (From: Daniel Schoo) This seems to happen mostly on machines with a lot of play time. There is supposed to be an air film between the tape and drum to facilitate the reduction of friction. When the drum gets worn and polished the air is squeezed out and the tape sticks. Little can be done for this. You could replace the drum but this is expensive and not worth the effort for most machines. The other option is to try and rough up the drum surface by light sanding with 3M Scotchbrite(tm). I don't need to go into detail about how difficult this is to do correctly but what the heck you don't have anything to loose. Just be careful and stay clear of the heads. BTW I have seen "cleaning" tapes that rough up the drums very well! Picture jittering vertically may be similar problem. Tape is not moving smoothly over the head drum.
Check whether the backtension on the tape is applying so much pressure to the drum that it is slowing it down. Backtension should be just enough to keep the tape in good contact with the drum. If it is too tight, then you backtension felt may be worn or adjusted too high. There is a lever just as the tape exits the cassette - push this to the right to reduce tension. Someone may have attempted to repair a broken backtension band and reduced its length - I got a VCR for repair once where this was done. If it is not the backtension, check free rotation of the drum when it stops - I bet it turns as freely as always. Could be a part in the motor driver that is faulty and failing when hot. However, the bearing could be worn or dry which would require disassembly and lubrication or replacement of the lower cylinder (assuming this is where the drum bearings are located).
Typical symptoms: front panel display is active, it may be possible to
set the clock or timer and change channels, but all transport related
buttons are totally inert. Perhaps there is no response to any button.
The VCR may or may not refuse to accept or eject a cassette.
This could mean many things including motor problems as well as a general
power supply or control system failure. However, here are a several things to
try first:
0. Check for cockpit errors - Someone may have accidentally set it for 'timer
record' or in 'parental lock mode'. Is there a little clock or key symbol,
'L', (or something else you don't understand) displayed? Inspect the
position of any slide or push-push switches.
* Timer mode may be set by a pushbutton, push-push, or slide switch, or from
the remote control.
* Parental lock is usually accessible only from the remote control. See the
section: "VCR shows LOCKED in the display".
Consult your user manual if in doubt about how the thing is supposed to
work!
1. Cycle power - unplug the VCR from the wall (don't just use its power
switch) for a minute or two to see if the microcontroller simply got
into a confused state. This is more common than you would think. A
random power surge can do it. The VCR may have gotten into a bad
(mechanical or electrical) state.
2. Unplug the VCR and remove the covers. Rotate the shafts of each of the
motors (cassette loading and tape loading or main motors depending on
your VCR) clockwise a couple of turns (assuming there is no resistance
to turning). Plug it in and listen for initialization sounds - it should
detect that the mechanism has been moved and then reset to a safe position.
See if it is now behaving.
3. If (2) doesn't do anything, try several turns counterclockwise instead.
4. If still no improvement, there may be more serious power supply, motor,
or control system problems.
If any of these appears to solve the problem, it is quite possible that you
will never experience it again. However, a dirty mode switch (see the
section: "VCR mode (sensor) switches" may have resulted in an overshoot
to a bad mechanical state and without cleaning or replacement, the same
thing may happen again.
The clock runs either off the power line (zero crossings of the 50 or 60 Hz waveform) or from a crystal (possibly a reference derived from one of the other frequencies used elsewhere in the VCR). Conceivably, a bad backup battery or supercap might result in the clock remaining in setup or power fail mode. Unfortunately, this probably isn't much help since identifying and locating the relevant components will be next to impossible without a schematic :-(.
You turn power on or just plug in the VCR to the AC outlet and it goes through the whirring sounds of playing a cassette - but there is not cassette present. However, first try unplugging it for 30 seconds or so and plugging it in again. The microcontroller may just have had a bad day and gotten confused - either a bad reset or a power glitch. Assuming this doesn't help: This could be due to a faulty end sensor or a bad LED or light bulb that provide illumination for the end sensors. If either sensor's output is the same as when a cassette is present (blocked), it very likely that the microcontroller will be confused. In some designs, this is indistinguishable from a cassette actually being loaded. If the 'cassette in' indicator is on, then this is likely. BTW, if a VCR uses an actual light bulb for that central light source and it is not lit when you attempt to load a cassette, it is burnt out. The LEDs used in most modern VCRs are IR and invisible, however. With somewhat similar symptoms, it is also possible that the VCR is not able to complete the startup initialization due to a slipping belt, gummed up lubrication, or other mechanical or motor problem. The clincher would be if you manually load a cassette (by turning the appropriate pulleys, etc. with it unplugged) and it then plays the cassette properly and acts normally until you try to eject. However, don't try this unless you are sure of how the mechanism works as it is easy to cause damage.
You press PLAY and the VCR gets halfway through loading the tape and suddenly aborts and shuts down. Or, you put a cassette in and it is immediately spit out as though it tasted bad to the VCR. Or, you press PLAY and the VCR goes into REWIND mode. Or, you pressed REVIEW and it ejected or attempted to eject the cassette. Before you break out the screwdriver or shotgun, cover up the IR remote sensor and cassette slot. Some types of electronic ballasted fluorescent lights may confuse the remote control receiver. Or, someone or something may be sitting on the remote hand unit or it may be defective and continuously issuing a REW command! Excessive general illumination may even make its way into the tape start and/or end sensors and trick the VCR into thinking the tape is at one end. (If you are working on the VCR with its cover removed, block any stray light from hitting the area of the tape transport to see if behavior returns to normal.) Assuming neither of these is the source of the problem: First, eliminate the possible mechanical causes such as slipping belts or a bad idler tire which could prevent the VCR from completing your requested action - it then shuts down or attempts to return to a 'safe' position. Bad connections are a possibility but not as likely as in a TV or monitor, for example. However, some VCRs (certain JVCs and clones, for example) ground parts of the circuitry via the circuit board mounting screws and simply tightening these are all that is needed to affect a cure. The microcomputer or its associated circuitry could be defective as well - but this is not as common most people fear. Occasionally, a faulty power supply may result in similar behavior. Its output voltages may be marginal, drop under load, or have excessive ripple due to dried up filter capacitors. However, a more likely possibility than any of the above is that a sensor assembly present on most VCRs called the 'Mode Switch' or 'Mode Sensor' is dirty or bad. See the section: "VCR mode (sensor) switches". Failure of the Mode Switch is a very common problem with numerous VCRs of many makes and models.
In order for the microcontroller in a VCR to confirm correct functioning and
completion of various operations like cassette and tape loading and roller
guide position, some mechanical sensor feedback is normally used. The most
important sensor assembly in most VCRs is called the 'Mode Switch' or 'Mode
Sensor'. The purpose of the Mode Switch is to inform the microcontroller
of the gross position of the mechanism at all times. For example, the mode
switch may have 5 positions:
1. Tape unloaded and cassette out.
2. Tape unloaded and cassette in.
3. Tape half loaded against A/C head but not around drum.
4. Tape fully loaded around drum and roller guides at V-Stoppers.
5. Pinch roller pressed against capstan - play/record position.
The microcomputer monitors the outputs of the Mode Switch continuously when
it is executing a mechanical operation (some monitor it at all times even
with power 'off'). If an operation takes too long to move from state to state
or an incorrect state transition occurs, the operation will be aborted and
an attempt - possibly several - will be made to return the transport to a
'safe' position - unloading the tape and possibly ejecting the cassette.
If the Mode Switch contacts are dirty or worn, or if it has somehow loosened
on its mountings and shifted slightly, one or more of these positions will
report back incorrectly or erratically signaling an error condition. For
example, a transition from state 1 to state 4 directly would totally confuse
the poor controller. A Mode Switch that shifted out of place (or where
other timing relationships in the VCR are messed up) might result in certain
operations stopping at the wrong position as well. For example, if the
Mode Switch shifts one way, the pinch roller may never quite press against
the capstan or the roller guides may not snuggle up to the V-Stoppers as
they should in play mode. If it shifts the other way, operations may fail to
complete and run against the mechanical stops - stripped or broken gears may
even the result.
A dirty or worn mode switch can result in cassette or tape loading, or
unloading or eject operations aborting and resetting or the VCR shutting
down. For example, some Emerson VCRs will move part way when loading and
then shut down. Repeated attempts may get them fully loaded and then PLAY
or other tape movement operations will work properly. However, unloading
will result in similar cranky behavior.
Mode Switches are usually linear or rotary slide switches with 4 or more
output terminals. They may or may not be easily accessible. On some, they
are visible once the bottom cover is removed. On others, they are buried
beneath a bunch of mechanical doohickies (technical term). Some are
removable with a screw or two and a connector. Others require desoldering
and the removal of a whole lot of stuff - all of which must be carefully
replaced with exactly the same timing relationships - just to gain access.
Once, you get at them, you can often snap apart the housing and use contact
cleaner on the sliding contacts and surfaces. I usually do not use any
kind of lubricant as it can gum up on the contact surfaces resulting in
erratic outputs - possibly the cause of the original problems in the first
place. Some may not come apart and replacement is the only option if
squirting contact cleaner through any visible openings does not help.
Note that without disassembly, there is no way of knowing if there is
still dirt or gummed up grease inside or if the contacts are actually
pitted. Conversely, if squirting in some contact cleaner does not help,
the mode switch may still be the problem since you have no way of knowing
how far the contact cleaner penetrated or whether it had any effect.
Sometimes, bad solder connections to the mode switch are the only problem.
However, be very careful about not moving anything and take careful notes
on the position of any parts that you disconnect as critical timing
relationships are controlled by the gear positions. Stripped gears or
other broken parts may result when the mechanism cycles. Also, in certain
positions, levers or sliders operated by the mechanism you remove may
spring out of position and you will need to make sure they get put back
into the correct slots in any cams when you are done. Mark all gear
positions even if they do not seem to be critical. See the section below
on how not to mess up your day by ignoring timing marks or more simply:
"Mechanical relationships in VCRs".
Note that if you experience erratic behavior with a VCR manufactured
by Sharp, the probability of a dirty mode switch is very close to 1.
See the section: "Erratic behavior of Sharp VCRs".
The complexity of the mechanism in a VCR can be quite intimidating. To avoid total frustration and really messing up your day, before you remove anything mechanical, take careful notes of precise relationships of any gear, lever, switch, anything that might possibly get back together in an ambiguous way. Often there are 'timing' marks on the gears just as you would find in a lawnmower or automobile engine. These will be little arrows or holes which will line up with stationary marks or with each other on adjacent gears when the mechanism is in a particular position. Often, it is best to put the mechanism in the position where the timing marks line up because there may be fewer levers, cams, etc. which are under pressure or tension in this position and thus fewer things to pop out at you. If there are no apparent timing marks, make your own with a scribe or pen. Sometimes mechanisms that at first appear not to be critical are obscured in such a way that they really control critical timing. So, when in doubt, make more notes than necessary - with diagrams.
This may mean that pressing on a circuit board, flexing a cable, or operating
the VCR in different orientation affects behavior. Sometimes this is affected
by temperature as well.
Note: if this only happens while servicing, confirm that excessive light is
not affecting the start/end sensors.
Do not confuse these sorts of symptoms with those indicating a faulty or dirty
mode (sensor) switch. See the section: "Erratic behavior in various modes".
* Unlike TVs and monitors which have high power circuitry and are prone to
cold solder joints from poor manufacturing or thermal cycling, most of the
circuitry in a VCR is low voltage and low power. Although problems with bad
connections to these components is relatively rare, visual inspection
should still be performed where erratic behavior is noted.
Exceptions include:
- Power supply regulator(s) or switchmode power transistor (depending on
type).
- Motor driver (power) transistors or ICs - particularly those for the
main (capstan/reel) drive and video head drum.
- RF, video, and audio jacks since they may be stressed mechanically.
* Internal multiconductor (crimp terminated) cable connectors. These may just
deteriorate with age and use. Clean and reseat the connector(s).
* Circuit board ground screws. One or more of the screws holding a circuit
board may also be providing a ground connections. These can work loose or
corrode. Remove screw, scrape corrosion, and/or tighten.
* Hairline cracks in circuit boards. If the VCR has been dropped, this is
very common. Sometimes, these are very difficult to locate visually but
locate them you must! See the section: "VCR was dropped".
* Broken or shorted wires. Some of the individual wires in various signal
cables are quite thin and fragile. Overzealous movement of circuit boards
while replacing belts or other maintenance operations can easily pinch
these resulting in immediate or delayed failure. This may also take place
when replacing boards. It seems that the manufacturers seem to make it
impossible to squeeze all the wires back in where they came from!
CAUTION: Always try to avoid pulling on the wires when removing a connector.
This will minimize stresses which could result in the wire conductor breaking
off inside the insulation - this would be very difficult to locate.
You were watching your favorite tape and suddenly the VCR emits a mechanical eek and is now dead - or you press eject and the VCR shuts down without regurgitating your tape. Worse yet, someone (we will not point fingers) forcibly removed the tape to return it to the video store. Assuming that 'forcibly' does not mean that permanent damage was done, then the first place, as always, to check is the idler tire and then all other rubber belts. At this point it is hard to say whether your problem was compounded by the removal of the tape. If any gears were shifted with respect to one another, parts bent, or springs sprung, then without a service manual, it would be difficult for a technician let alone someone not familiar with your VCR to repair it. An error at power on usually means that the microcomputer thinks that it is unable to put the mechanism into a 'safe' position. This could be due to slipping belts, broken gears, a bad motor, shifted sensors, or faulty electronics. The original symptoms may have been a slipping idler preventing the takeup reel from rotating allowing tape to spill into the machine. Power on problems may be more serious. See the section: "VCR is failing the power-up sequence".
Here is a true story of forced eviction of a tape and the consequences. :-( This teaches you two lessons: Don't use violence to remove a stuck cassette and mark all gear, lever, sliders, etc. timing relationships before you disturb anything! (From: AL (kb8wcq@tir.com)). "I have a Panasonic VCR (model PV-4820) that will not acknowledge tapes. The original problem I found was in the power supply. I replaced all the electrolytic caps, and the PS now works- all the outputs measure OK and the display and tuner controls seem to work OK. But once the PS went bad, it would not take in tapes, so the owner decided to force one in. He sheared half the teeth off of the 'link gear', which I replaced, but it still will not accept a tape. I can manually push a tape all the way in, with some resistance, until it sits down on the reels, but it is not acknowledged in any way. If I don't hold it down, it springs back out." It sounds like you possibly failed to retime the link gear in relation to the rack gear on the loader assembly. If that's the one I think it is and you have not timed one (of course this is something the average person does, say once a week? :-) --- sam) before, you probably should get the manual. Or try this: Remove the carriage assembly, turn the VCR on its side, press and hold the little height change lever (bottom side, near the solenoid), manually turn (CCW) the large belt-driven pulley until the mechanism is in the full eject position, note the position of the link gear, turn the large belt-driven pulley in the opposite direction until the link gear makes exactly one revolution, re-install the carriage (in the eject position) making sure the carriage gear and the link gear mesh properly. Other than that it's pretty simple... Assuming of course nothing was disturbed with the gears below the deck, and that the link gear, mode switch, pressure roller lift cam, etc', are in their proper position. Sounds simple enough! --- sam :-)
This often means that the internal microcomputer found the mechanism in
an unusual state and was unable to reset it. Some VCRs will actually
move portions of the mechanism to make sure that everything is ok
to accept a tape. Failure here may be the result of a slipping or broken
belt or a belt that has popped off of its pulleys, gummed up lubrication,
or some other mechanical fault. How old is it? Rubber parts tend to
become smooth and lose their elastic properties ('rubberiness') after
a few years. Does the VCR make any kind of whirring sounds before
shutting down? This would mean that it is attempting to move something
back into position. Is there a tape in the machine? How about a toy, peanut
butter and jelly sandwich, or a little applesauce? It could be a sensor
or other electronic problem, but check out the mechanical possibilities first.
On a VCR which has been cleaned and with good rubber parts:
VCRs have a light or LED (IR, infrared) in the middle of the mechanical
assembly that detects the end of tape. When a tape is loaded the
tape will cover the sensor. The controller can tell if the tape is at the
beginning, middle, or end by the sensor. The is achieved by a clear
leader at the beginning and end of the tape. The microcontroller will detect a
problem if the sensors do not detect the light or LED (middle of tape)
and the carriage assembly is up (no tape loaded). The VCR will shut down.
1. If you have an incandescent light and it is not lit, it is burned out.
If you have the LED type you can buy an IR tester from an electronic
parts supplier or construct one as described at the end of this document.
Replacement LEDs are readily available.
2. The VCR might be in a confused state. Many VCRs have a belt that
drives a loading motor. This is the motor that drives the tape around
the heads. If those guides are not fully retracted, the VCR shuts down.
Check the belt and replace if necessary.
3. Ensure the tape guide assembly is fully retracted by physically turning
the appropriate gears.
4. Some obstruction is preventing part of the mechanism from resetting.
Visually inspect for foreign objects or rough edges on something preventing
full movement. Dried up grease can also cause this.
5. A gear has slipped a tooth and one part of the mechanism does not track
another. This may happen if a tape was forcefully ejected after being
eaten. You may find that a tooth has actually broken off.
6. If this occurred after having disassembled part of the mechanism, confirm
the timing relationships. Make sure belts are installed in the correct
locations - and on the correct sides of any intermediate pulleys where
belts link more than two pulleys.
Without a service manual, determining the correct relationships for all
gears may be impossible, but if only one has slipped you may be able to
locate timing marks near the edges of the gears which should line up -
usually when the tape is unloaded. (portions from michael@marconi.nsc.com)
Your VCR has worked fine for several years but now you get the 'DEW' warning in the display and no tape functions work. The dew sensor is intended to prevent operation of the tape transport if the humidity is so high that moisture would build up and cause the video tape to stick to the rotating drum and damage the heads or get hopeless tangled as a result. First, perhaps the dew warning is telling the truth. If you have just moved the VCR from a cold area to a warm one, let it sit for an hour or so and see if the dew warning goes away. If you just fished it out of the toilet or scraped stewed peaches from the interior, well, dew may be the least of your problems. Assuming that there is no reason for a dew warning, the dew sensor may be bad or have changed value. There may or may not be an adjustment for this. Before you go inside, try unplugging the VCR to clear any spontaneous fault condition - see the section: "VCR has gone whacko". The dew sensor is a resistor that changes value when there is condensation. If the sensor is bad, you should be able to replace it with a resistor and keep the VCR happy. You should be able to determine the appropriate resistance by trial and error. If it is the type where the resistance decreases with moisture and the controller does not care if the resistance is too high, then you can just remove it. Either way, you have now lost the protection that the dew sensor provides. Replacement is obviously best. Don't overlook the possibility of a bad connection - it may be plugged in and just need to be reseated. One type looks like a ceramic board, maybe 1/4" - 1/2" on a side with a silver/gray printed circuit pattern. If the A/D or whatever is used to determine when there is dew is faulty, then you will most likely need a service manual to troubleshoot it.
You go and try to play a tape and the VCR displays the word 'LOCKED' or perhaps just a flashing 'L' in the display. This may mean that the VCR has somehow been programmed to prevent use by unauthorized kids (you are not reading this if you are a kid, right?) Even if your model does not have this feature, the same basic chassis is probably used for a range of models so it could have gotten into a confused state. * Sometimes, just pressing the PLAY, POWER, VCR1, VCR2, (or other much more obscure) button on the remote control (it may be designed not to work from the front panel) for 10 to 20 seconds will clear this mode. Some remotes have a little 'key' symbol. How logical! Press it. * Unplugging the VCR for a minute or two may work. Unplugging for long enough to drain the backup battery will probably work but you may then need to reinitialize the clock, channel selection, and programming. * Best bet is to check your instruction manual (you can locate your user manual, right???).
Suppose your just-out-warranty VCR is now acting up for no apparent reason - making strange sounds, forgetting its programming, refusing to cooperate, etc. I don't know what kind of recourse you may have as an unsatisfied consumer, but I would try to get some resolution through your place of purchase. Such a VCR has all the symptoms of Alzheimer's disease - it should not be failing in these ways so early in life unless it is under penalty of hard labor in the damp snake infested dungeon of an English castle! Or it has been the depository for peanut-butter-and-jelly sandwiches, applesauce, or marbles! All the usual recommendations of cleaning and checking rubber parts and so forth apply to units that have seen significant use or are a few years old or both. Something this new under normal use should not be causing this amount of grief. However, sometime I wonder whether using a machine very little contributes to problems. First try your place of purchase - there may still be some degree of interest in maintaining customer satisfaction. If you have given up on the store, start by checking the rubber parts for dust and deterioration (with that kind of use, dirt should not be a problem, but dust or smoke can accumulate), check for adequate lubrication (but don't add any unless it is definitely needed and then only the smallest amount - VCRs do not need much oil or grease and too much will just compound your problems - and check for foreign objects especially if there are small kids about.
You may think you are on the set of the latest sci-fi movie. The VCR displays are counting at random, pushing buttons produce unexpected results, motors may be spinning, or the VCR may be repeatedly loading and unloading a non-existent tape. I may be attempting to play a tape even without you pressing any buttons. While these could be symptoms of a actual problem, first try unplugging the VCR from the wall outlet (don't just turn it off) for a minute or so. If this does not help, try unplugging for a couple of hours - this will usually drain the backup battery and reset many other functions of the VCR. If one of these techniques results in the universe returning to normal, there may have been a power surge or lightning strike nearby which threw the microcontroller into a confused state. It may never happen again. However, power surges can be the result of heavy appliances like air conditioners on the same circuit. If this is the case, you should consider using a different circuit for your electronic equipment. If this behavior started when the VCR was just plugged in or following some other action requiring the mechanism to move or initialize, check for mechanical problems like a broken belt or one that has popped off its pulleys or an obstruction like a rock or toy that is preventing the VCR from completing the required motions. Also see the section: "VCR is failing the power-up sequence". Once you have ruled out mechanical problems, it is likely that the VCR has a microcontroller, power supply, or other electronic problem which may require professional service.
Normally, the AC line provides power to retain the clock, active channels, and programming settings. During a power failure, the clock and programming is usually powered using a supercap or battery (usually rechargeable). Channel settings for older style varactor type tuners were often stored in some kind of non-volatile memory while active channels for quartz tuners generally use battery backup. The clock and programming backup may be a supercap - a very high value special electrolytic capacitor - as much a 1 F (1,000,000 uF) at 5-12 V. Alternatively, it may use a rechargeable NiCd battery. In either case, these are easily replaceable with standard parts. A NiCd battery pack of similar ratings should be readily available. Supercaps are available from large electronics distributors. NiCd batteries fail in two ways - loss of capacity or shorted cells. If memory is retained for a much shorter time than it used to, then the battery has probably lost most of its capacity. If you measure less than n x 1.2 V for an n cell NiCd battery pack after it has been charging for awhile, there is likely a shorted cell. In either case, the best solution is a replacement though the various common techniques for rejuvenating NiCd battery packs can be attempted (remove from VCR first!). The non-volatile memory could use a special chip like EEPROM which does not require power or a battery backed SRAM or be internal to one of the VCR's microcontrollers. Channel memory may use a separate power source from the clock and programming, possibly a Lithium battery since it is undesirable for the channel settings to be forgotten even if the VCR is unplugged for a month or more as it is such a pain to reinitialize them. Rechargeable batteries have too high a self discharge rate.
This usually means that one or more of the voltages to the vacuum fluorescent display (VFD) are missing or that the display controller is bad. If the front panel suffered physical damage, the display tube, circuit board, or other components could be damaged. The VFD requires around +30 VDC for the tube anode and 4 to 6 VAC or DC for the filament. Its cathodes in the form of character segments or formed words or symbols will likely be driven directly from one of the controller chips. Remove the front panel and with the VCR plugged in, turn out the lights and inspect the filament, several very fine wires running the length of the display. They should be glowing a very faint red-orange. If you see nothing, the filament voltage is likely missing. Filament voltage may come directly from the power transformer (if a non-switching type power supply) or be one of the DC outputs of the supply. Check around the VFD for the +30 VDC (approximately). If this is missing, there will be nothing displayed. In some VCRs like those manufactured by Hitachi, a separate DC-DC converter module provides power for the display only. See the section: "Dead clock in Hitachi manufactured VCR". Look for bad connections, open resistors, blown IC protectors or fuses, etc. Of course, if the VCR has an on-screen display, you will be no worse off than many newer models that have done away with the front panel VFD entirely! (From: Paul Grohe (grohe@galaxy.nsc.com)). The fluorescent display in most VCR's require three voltages: 1. The filament requires a floating 3 VAC. 2. The filament has to be biased at -12 V to -15 V 3. The segments need -20 V to -30 V to light. The DC-DC converter usually provides a "floating" 3 VAC winding, a low current -12 VDC tap connected to one of the filament leads, and a -20 VDC to -30 VDC segment drive voltage. If you look really, really closely at the display, you will see the faintly glowing filaments stretching across the length of the display.
First, don't ignore the possibility that you are attempting to play an old, worn, or defective tape. This is especially true of rental tapes which have been through who knows what kind of VCR hell. The control and audio tracks - along the edges of the tape - are the first to wear. Weak muddy sound and erratic tracking are also common symptoms caused by old worn tapes. There have even been instances of new name brand tapes which were cut too wide - though this would be extremely rare. To confirm that it is your VCR doing the dastardly deed, play or record for at least a minute on a tape known to be in good condition. The use REV to back of the tape for about 15 seconds. Eject and open the cassette door by releasing the latch and inspect for edge crinkling. Any rippling along either edge of the tape is an symptom of a possible problem. It isn't only that the tape does not make good contact with the audio or control head (depending on which edge is damaged) but just an indication that the tape may not be moving through the transport precisely positioned. Assuming you are having the same problem on multiple tapes and that using a known good (new) tape results in damage: This is an indication that your tape path alignment is off or your rubber parts (probably the pinch roller) need replacing. The tape is wandering up and down as a result of unequal pull from the capstan due to a glazed/worn pinch roller. There could also be other aspects of tape path alignment like roller guide tilt (which is probably not adjustable), A/C head tilt, dirt, roller guide height (don't mess with it), etc. See the chapter: "Tape Path Alignment and Backtension Adjustment. It could also be worn feet on the roller guide assemblies causing the guides to not be perfectly vertical. Replacement of these parts may be the only cure. Other much less likely possibilities: excessive or varying backtension, tight idler clutch, electronic problems. For a VCR with very high mileage, it is also possible that there has been a ridge worn in the surface of the control head preventing consistent contact between it and the tape: (From: Phil Reed (100555.244@compuserve.com)). "One thing that can happen is that the control track head gets a ridge on it (due to wear) which prevents the tape making good contact with it. This can make the tracking go mad and sometimes even mute the video. Pausing the VCR overrides any muting, resulting in a clean still picture. Another clue is that some tapes will do it worse than others, this is due to slight variations in tape width or condition." Other related symptoms include: * Sound does not always appear at full volume or normal quality for a few seconds after the VCR starts playing. It may vary in loudness during play as well. Slightly changing backtension may make a big difference in audio. * If your VCR has autotracking, its indicator may be flickering as the logic attempts to solve an impossible problem. * On HiFi VCRs, there will likely be no HiFi sound as its tracking is even more critical than video tracking. * Tape speed may be changing resulting in wavering sound or even running (usually) faster than normal. This may be due to the control head not reliably reading the control track. If you look carefully, you should be able to see the tape wandering slightly producing the muddy sound and erratic tracking. The tape may not be perfectly smooth in passing over the various guides and rollers. Normally, you will almost not be able to tell the tape is moving at all except by examining the reel rotation - it is that mirror smooth. First, clean the tape path properly, especially the capstan and pinch roller, tape guides, A/C head. Inspect the pinch roller for glazing, cracking, etc. and replace if necessary. See the sections: "General guide to VCR cleaning and rubber parts replacement" and if necessary, the chapter: "Tape Path Alignment and Backtension Adjustment". Another possibility is that the control portion of the A/C head stack is dirty or defective or there are problems in the wiring or its circuitry. Double check that the tape is in solid contact with the bottom of the A/C head stack (where the control track is located), that the head is clean, its connector is clean and seated properly, and look for any broken wires or bad connections.
Normally, speed is controlled via phase locking the capstan to the 30 Hz control pulses read off of the tape via the stationary audio/control head. On a VCR with autotracking, the autotracking light may be flickering as well. Possible causes for loss of lock: * Dirt or bits of tape or oxide on control head - clean and inspect. * Defective control head. Try making a recording. If recording plays normally on another VCR, then control head is probably ok. * Tape wandering up and down so that control track is not sensed properly (how is the sound - this would also cause fluctuating or missing sound.) See the section "VCR randomly switches speeds, tracking problems, and muddy sound". * Mechanical fault preventing firm tape-control head contact such as a stuck movable guide post. * Mechanical or mode switch problem preventing firm capstan-pinch roller contact. Under certain conditions - possibly at the beginning of a tape when takeup tension is greatest - the takeup reel may have enough torque to pull the tape past the video heads without the capstan controlling the speed as it should. * Defect in servo or control circuitry or power supply (voltage out of tolerance). * Bad tape. Don't overlook this possibility especially if it is a old or rental tape. The control track may have gotten erased or warn off - it is at the edge of the tape. Try another tape. Inspect the tape path really really carefully to determine if there is some obstruction preventing tape-control head contact or other mechanical problems. Try cleaning the tape path and checking the rubber parts. Check power supply voltages if you can determine what they should be (see the section: "VCR power supplies". If these procedures to not reveal anything amiss, you will need a service manual to pursue electronic faults.
As always, rule out the possibility that this is just a bad tape. There have even been instances of new name brand tapes which were cut too wide - though this would be extremely rare. It could have been creased by someone else's VCR. Try a tape you can afford to sacrifice (though it will still be safely usable) and run it through the VCR. Sometimes, there will be a problem only near one end so you will need to try it at various sections of tape. Record a few minutes and then back it up a bit and inspect for damage by opening the cassette door (press the release on the side). Both edges should be perfectly flat and smooth. If you get similar playback symptoms with this cassette and/or find that the tape is being creased along one or both edges, then it is your VCR doing the dirty work. When the bottom of the tape gets creased, the control head may no longer align with the control track and you loose servo lock on the sync signal. Your audio may be fluctuating in intensity as well since the audio track is wandering also and the tape may be intermittently going in and out of correct tracking and/or changing speeds. Since the tape can no longer seat stably on the lower drum guide ridge, there could be other problems such as noise bars along the top or bottom of the picture, jumping, etc. It could be the guide posts or other tape path components, but before you turn every screw you can find and make the problems hopelessly worse, replace all of the rubber parts - belts, idler tire, pinch roller. And while you are at it, give the machine a good cleaning. A dirty, worn, hard, dried out pinch roller in particular can result in the tape wandering up and down causing tracking problems and creasing the tape in the process. This is probably the most common cause of tape damage assuming the VCR itself has not been abused (i.e., jammed cassette removed using a pair of Vice-Grips(tm)). With a thorough cleaning of everything before buying the new rubber (which BTW should not be more than a total $10-$15 from a place like MCM Electronics), you may at least see a temporary improvement in performance - and confirmation of the diagnosis. You really need to determine exactly where the tape is being creased. Once you do this, you may be able to determine the cause and visually verify whether the problem is affected by any of your adjustments or probing. Some other possibilities include: * Worn feet on the roller guides causing them to not be precisely vertical. Sometimes there are adjustments for tilt; usually there are none. Sometimes replacements are readily available (especially if this is a common problem with your model). * Cassette not seating properly. Press down on cassette while playing a known good tape. If it moves, then check for obstructions or foreign objects such as toys or peanut butter and jelly sandwiches! A dirty, oily, or just tired belt may not grip well enough for the mechanism to complete the cassette load cycle. * Oil seal washer on bottom of capstan has worked its way up out of place. Carefully push it back down and then clean the capstan shaft. * Various guides too high or too low but this is pretty unlikely unless they have loosened somehow. Don't adjust unless you have a service manual or are absolutely sure that they have changed height. * Backtension misadjusted (usually too great). If the tape passes around the backtension lever at too straight an angle (it doesn't bend enough), in addition to the possible incorrect (excessive) backtension, it may simply not seat properly when passing around the subsequent guidepost or impedance roller (that white plastic wheel that doesn't seem to serve any purpose).
Symptoms may be that the tape counter stops moving and/or the VCR enters stop mode and shuts down. Assuming this is not a mechanical problem - bad idler, belt, etc., make sure you don't accidentally have an 'insert editing' mode enabled. Insert editing uses the previously laid down control track as the timing reference. This provides clean glitch-free transitions between scenes. Insert editing will not work at all on a new or bulk erased tape. If you routinely use your cassettes over and over, there will be varying amounts of previously recorded material - with control tracks - on the tapes. At some point your recording may start to use tape beyond the recorded sections and - presto, no more control track. Poor VCR is confused and aborts.
Make sure you are using the proper record button. Most VCRs have a OTR (One Time Record) or 'quick record' feature which starts just like normal record stops after a multiple of (usually) 15 minutes depending on how many times you press the button. The (normally) red button should be used for unrestricted untimed recordings. Some VCRs also have other timed modes - sort of like the timed off function of a clock radio. Pressing the 'Off-T' button adds time to record or play in 15 minute increments and then the VCR shuts off.
The result may be inconsistent positioning of the tape if you use the counts to locate programs. It might also result in the VCR aborting PLAY, REC, FF, REW, or search modes if it thinks that the counter is not changing as expected - missing pulses or skipped counts. For real-time counters, this may mean a problem deep in the electronics requiring a service manual. However, if you are attempting to play a tape that has nothing on it, the real-time counter will not change. This is normal as there are no control pulses on the tape. For non-real-time counters, if the display skips counts or 'free runs' - counts very quickly at certain times, this could be due to a defective sensor or hysteresis circuit. If it counts in the wrong direction, a logic problem is indicated as direction is determined by the microcontroller being aware of what mode the VCR is in - there is likely no actual direction sensing on the reel. See the section: "Reel rotation sensor testing" for further information.
If the VCR works in all respects when tuning broadcast or cable channels but playing a tape results in no picture, a very snowy picture, or just a blue screen, there may be problems with the video heads, the lower cylinder, head preamps, or other video electronics. Testing most of these is beyond the scope of this document and will require a service manual and test equipment. However, you can do a decent job of determining if the video heads are likely to be at fault. Sometimes, when snow or serious video noise suddenly occurs while playing a rental, old, or damaged tape, it means the video heads have picked up some oxide and are no longer making good contact with the tape. Letting the VCR play a newer tape for a few minutes may clear this if it is minor. However, video head cleaning (using a cleaning tape or the manual procedure described in the section: "Video head cleaning technique") will probably be needed. But, first start with the section: "Snow on one or more speeds" and NEVER NEVER attempt to clean the video heads without using one of the recommended techniques - you can easily destroy the heart of your VCR! Also, never attempt to play or record on a spliced or seriously damaged tape as this can also result in destruction of the video heads.
If attempting to record results in unexpected behavior, there could be a variety of causes depending on what you get for playback: * Attempts to record are ignored by the VCR or cause the cassette to be ejected. This may mean that the record protect tab on the cassette is broken off or the record tab sense switch is dirty or bad. * Record (either manual or timer) stops at random times - possibly with flashing display and/or ejects cassette. This could be the result of a dirty or defective record sense switch or misalignment preventing proper engagement with it. Some VCRs check for the record tab constantly while others just check when the REC button is pressed or the timer initiates record. It could also be a defective reel or tape end sensor halting record though these would likely affect playback as well. * Playback results in video snow and whatever was on the tape, if anything, is gone. This means that the old recording is being erased (if there was one) but nothing or too weak a signal is being written by the video heads. This could be due to a variety of electronic faults as well as marginal or bad video heads. * Playback results in a picture but it has a wiggling rainbow pattern running through it. This is normal at the start of a recording made on top of an old recording if your VCR does not have a flying erase head. However, it should wipe down the screen in a few seconds and disappear. If it does not go away, then your full width erase head is not working. * Playback results in a flickering picture alternating between good video and snow at the frame rate (about 30 Hz for NTSC). This could mean that one of the two heads used for record is dirty or defective. * Playback results in proper video but the previously recorded or no audio. The audio dub switch (if any) may be in the wrong position or the audio circuitry may be defective. * Playback results in a picture which is cycling in brightness or flashing. This likely means that you are attempting to record (copy) a Macrovision(tm) (see the info at: http://www.repairfaq.org/~filipg/LINK/F_MacroVision.html) or some other copy-protected tape or your cable or satellite company is transmitting copy-protected video. Some of the new digital DBS satellite receivers output a Macrovision copy protected TV signal so you can't tape the movies from them either. Newer VCRs will generally not record successfully. Some older VCRs will record without problems. See the section: "Why VCRs will not copy (Macrovision) copy protected tapes". (8mm VCRs may record the entire signal and therefore be able to playback successfully. However, attempting to copy the 8mm tape onto a VHS tape will result in the same problem.)
Did the problem happen suddenly? Or develop over time? If suddenly, what were you watching at the time? A (literally) dirty rental movie? If this VCR has 4 or more heads, SP and EP may use a different set of heads, so certain heads may still be dirty or bad. If the machine tracks perfectly in EP, then alignment is probably fine - EP is more critical as to alignment as the EP track is 1/3 the width of the SP track. Have the video heads been cleaned using the proper procedure (not just a cleaning tape - see the section: "Video head cleaning technique"). New video heads may fix this, though it can be caused by other problems such as weak read electronics. See the chapter: "Video Heads and Upper Cylinders". You should also check the backtension adjustment - if too loose, head to tape contact will be compromised. Try increasing it momentarily by pushing the backtension lever slightly to the left while the tape is playing. The usual way to adjust backtension without a backtension meter and service manual is to look at the image just before vertical retrace at the bottom of the screen - this is normally not visible unless you can reduce vertical size or play with vertical hold to get the vertical blanking bar to appear. Of course, most modern TVs don't have any such controls! This is the head switching point and when the backtension is properly set the image above and the bit of image below this break will be approximately aligned. If increasing backtension helps, either the heads are marginal or the back- tension was low. However, low backtension will usually show up as a waving or flagging effect at the top of the picture.
This means that there is one or more horizontal lines during playback that are at fixed locations on the screen. These could be the result of electronic problems or marginal video heads but the possibility that should be explored first is that of tape damage. If a prerecorded tape that plays properly on another VCR, shows the effect on the suspect VCR - AND - then shows the same thing on the other VCR, it is being damaged by something in the tape path. Open the door of the cassette by releasing the catch on the side. Look carefully at the surface of the tape - it should be mirror smooth all across. If you see any evidence of hair fine (or larger) scratches running the length of the tape these are what are causing the line. This is likely a result of a bit of debris or a rough edge on one of the guide posts in the VCR. Get a brand new tape or a known good tape (that you can afford to mess up) and test it on another VCR (at the tape speed that is worst, if this matters). Assuming playback is fine, play it on the suspect VCR for a couple of minutes. Pull the plug (DON'T hit STOP) so the transport remains in the fully loaded position. Now, carefully examine the surface of the tape all along the tape path (disturbing its position as little as possible) to identify the location where the damage begins. It may just be a bit of something stuck to a guide post. Has the VCR been cleaned in the last 10 years? Note: This sort of damage to the tape does not represent a risk to your VCR's video heads so you can continue to use the tape if desired.
You have a VCR with known good heads that produces jumpy (vertically) video in play that cannot be stabilized with the tracking control. Perhaps you have attempted to adjust the mechanical tracking and maybe some other stuff. Some questions: * Did you replace the heads? Could you have gotten them 180 degree rotated from the correct position? I don't know what the implications would be on your model VCR, but there is a definite right and wrong on this. It would certainly show up as tracking being way out when attempting to play back tapes recorded on this VCR on another machine. * Exactly what adjustments did you touch? * Have you verified that the roller guides are fully engaged against the stops? * Have you checked backtension? * Did you touch roller guide height? This is probably a mechanical problem, most likely an adjustment or fault related to tape path alignment. However, it could also be due to electronic problems with the video or servo circuitry. The vertical sync could be corrupted or the head switching point not set correctly. The head switching point is 6.5 lines before vertical sync. If this ends up moving into vertical sync for some reason, you will get unstable video. The supply side roller guide height adjustment is also critical and would be the first thing to check mechanical alignment problems are suspected. However, don't overlook the obvious: your TV is marginal or misadjusted or you are attempting to play a bad tape.
Note that on a 2 head VCR, it is not possible to display a noise-free picture on a tape recorded at the SP or LP speeds. Therefore, for rental or pre-recorded tapes, what you are seeing may be normal. A 2 head machine should execute these special effects perfectly fine with EP(SLP) recorded tapes, however. VCRs with 4 or more heads will usually have a V-Lock adjustment - either a knob on the front or rear panel, or sometimes 'conveniently' accessible from under the VCR. Sometimes, a special tool is needed to adjust this control. Where tracking is adjusted with a set of +/- buttons, these may also be used in PAUSE mode. There may be separate adjustments for SP and EP(SLP) speeds as well. In any case, these settings are made while viewing a tape recorded at the appropriate speed in PAUSE mode. For LP speed - which is being phased out by many manufacturers, at least for record - these special effects usually do not work well if at all. This is basically due to the nature of the sync signal alignment on tapes recorded at LP speed and would require complex circuitry to handle properly at anything other than normal LP play speed. (If you care, the sync tips between adjacent tracks align on the tape in SP and EP recorded tapes but are off by 1/2 line with LP recorded tapes. This results in the tearing seen in search modes with LP recorded tapes.) Since this tape speed is of little true value - it is a compromise anyhow - the added expense has been found not to be justified except on professional machines.
This may be a 'feature' of your VCR. On some older models, the designers in their infinite wisdom (or that of their marketing departments) decided that no picture or no search capability at all was preferable to a picture with serious noise bars or one which didn't sync properly. This was usually before the days of 4 head VCRs which directly addressed at least some of these issues. Most 2 head VCRs will work fairly well on EP recordings but show noise bars over about 50 percent of the picture with SP recordings. For those made at LP speed, tearing will occur in addition to noise bars if they sync at all. Few VCRs deal properly with LP search as substantial additional circuitry is required. In my opinion (IMO), any picture is better than a blank screen or no search capability.
Problems will be similar to the following: "I have a General Electric VCR model VG4217 that's displaying the most unusual problems. When I play back a pre-recorded tape from a video store it plays fine. When I play back a tape recorded on the machine I get video noise for 4 seconds then clear pix, then video noise for 4 seconds, then clear pix and so on. I also noticed that if I have the tape counter displayed on the screen, and when the counter progresses its count, the tape plays properly. Then all of a sudden the counter stops counting and the problem continues again. I have cleaned heads well, cleaned tape path, and even cleaned the underside of the takeup reel, all to no avail?" First, make sure the tapes are in good condition. They may have been damaged (edge crinkled) before you serviced the VCR. This is now causing your erratic behavior and there is nothing wrong with the VCR. Before considering drastic action, record on a brand new tape - from end-to-end if the initial results seem promising. You may have a non-problem. Try recording you your VCR and playing back on another one. If this works, then bad tapes are the most likely explanation. If this does not work, there could be electronic problems: (From: Stephen Isaacs (stephen@myna.com)). The normal playback of a pre-recorded tape suggests most things are working fine. The self recorded problems point to a faulty control track recording system. bad oscillator, or amp. It is also possible the erase head is not doing its job making it difficult to record a new control track over an old one. (From: Richard (vcrtips@mail.vii.com)). Almost all pre-recorded tapes are recorded at the SP speed. If you are like most people, you probably do your recordings at the EP speed (to get as much on the tape as possible). Do you have the same problem if you record at SP? Your VCR probably uses different heads for SP and EP. You may have dirty EP heads, defective EP heads, a head amp problem. Or, there could be a tape tension or other mechanical problem. (From: Frank D. Ralston (fdr@continet.com)). Check the following: * Dirty (or worn) heads * Low back tension (common problem) * Tape path alignment (particularly input tape guide)
Symptoms like a picture which has a portion that is noisy or missing, or where the picture is split between top and bottom with the vertical blanking somewhere in between may indicate a problem with the PG sensor. The rotational position reference for the video head drum is usually supplied by a pickup in close proximity to the edge of the lower cylinder (probably) which has a small magnet fastened to it. This generates the so called 'PG' pulse and is used by the servo circuitry to properly control the drum rotation and the head switching point. If this sensor is moved or if there is a fault in the PG circuitry, a variety of record or playback problems can result. Without this reference, the servo circuitry has no way of knowing where the A and B heads are at any given time. During record, this may result in recording video which is not properly lined up with the video tape - a track may consist of the end of one field and the beginning of the next rather than an entire fields as it should. During playback, the head switching point may occur at the wrong time resulting in a partially snowy or missing picture since a head that is not even in contact with the tape may be active. Similar problems may make look like your TV's vertical hold control is set incorrectly with the vertical blanking bar visible at an arbitrary point on the screen. The assembly on which the rotating magnet(s) are mounted and the upper cylinder may be secured with one or two set screws. If these loosen, the the precise relationship may be lost resulting in a shifted head switching point. It may even be random - changing location each time the drum starts up due to the inertia of the upper cylinder. If this is the case, you will need a service manual to properly adjust the angular location of the magnet assembly unless there are obvious 'timing' marks to guide you. Beyond confirming that the pickup coil is in close proximity to the drum, the rotating magnet and sensor are secure, and that there are no bad connections or loose connectors, there is not much to be done for these problems without a service manual. The definitions below are just For Your Information (FYI): PG - pulse generator. The pulse is derived from the rotation of a magnet on the video head drum past a sensing coil. I suppose this could be done optically as well. FG - frequency generator. This is a signal (sine or square) derived from the rotation of the video head drum. This may be phase locked to the PG pulse but can be a multiple of the frame rate. This could also refer to the capstan or reel rotation rather than the head drum.
Unless your VCR has a flying erase head - located along with the normal video heads on the rotating drum - you will see a faint rainbow pattern near the start when recording over a previously used tape. The reason is that there is a separation of a few inches in the tape path between the video heads and the full width erase head. When you start recording at an arbitrary point, it takes several seconds (actual time depends on recording speed) totally erased tape to make it to the video heads. You are seeing an interference pattern between the old and new video signals. The pattern will slowly wipe from top to bottom as the diagonal tracks of new video intersect more and more of the erased tape. This effect will not occur (except possibly at the very beginning of the tape) as long as you record from start to end without backing up the tape at any time. If the rainbow pattern is present whenever recording over previously recorded tapes and does not go away, then your full width erase head is not working. This could be due to an electronic failure or simply a bad connection to the full width erase head. Alternatively, a mechanical problem such as a broken or popped spring or gummed up lubrication might prevent the pivoting full width erase head from contacting the tape properly.
Some rainbow patterns are normal for the first few seconds of recordings made on previously recorded tapes on non-flying erase head VCRs. See the section: "Rainbow pattern in recordings made over previously recorded tapes". However, alternating bands of rainbow or color indicate a fault sometimes referred to as 'barber poling'. This is likely an electrical fault in the chroma playback circuitry buried deep in the bowels of your VCR. The chroma reference is not locking or is locking erratically with the chroma signal. Unless you can find some bad connections or other obvious problem, this will be difficult to troubleshoot without schematics. Don't be tempted to twiddle internal controls even if they appear to deal with color - you will just mess things up for whoever finally repairs your VCR!
You have just loaded a videotape sent to you from your long lost cousin and you notice that the top of the picture is wiggling back and forth. First, if this wasn't the original complaint, make sure the flag waving problem exists with the TV that will actually be used with the VCR - it may just be your test TV or monitor that is unhappy. (Parts of the following from: Andrew Morphitis, Andrew@andrewsm.demon.co.uk). This fault is sometimes known as flag-waving when associated with video recorders. If the tape back-tension provided by the tension arm and supply reel-table is not the same as the back-tension provided when the tape was recorded (possibly on another machine) then the field timing of the video tracks being played back will be inconsistent . Your back- tension can be checked using a back-tension cassette gauge (a typical reading would be about 35g-cm for VHS) or you could adjust the back tension using a known good test tape (or reliable pre-recorded tape) until the waving disappears. If your back-tension does turn out to be incorrect and you adjust it according to the manufacturers spec. then all of the tapes you have previously recorded will probably still exhibit this waving problem - adjust to spec. or to your tape library - take your pick. Thats the theory - now the practice. Back-tension refers to the tension of the tape over the head drum, this is provided by the felt covered metal band (tension band) which is wrapped around the supply reel (left-hand reel from the front), the friction providing the tension. There are usually two adjustments associated with back tension and these can be found near the opposite ends of of this tension band, the tension arm operating position and the anchor point of the band. Adjusting the latter position will increase or decrease back tension (you will want to increase your back tension which has dropped due to excessive wear on the belt). If you do give it a bash then be aware that poorly adjusted back-tension can, at worst, give rise to premature head wear. Because of the differences between the back tensions of different machines, all modern TV's have a dedicated video channel button (usually channel 0) which has a shorter flywheel line-timing duration allowing the TV timebase to lock up more effectively to unstable video sources such as video machines. Are you using the video channel? - try playing the video through different channels on your TV.
There can be several non-electronic causes for poor quality sound on linear audio playback: 1. The audio head needs to be cleaned. A cleaning tape may not be effective. You can use Q-tips and medicinal or pure isopropyl alcohol or tape head cleaning solution. You might as well clean the tape guides as well while you are at it - a speck of dirt can cause the tape to wander and produce erratic sound. 2. The audio/control head needs to be aligned - particularly the azimith adjustment which is the angle the head gap makes with respect to the direction of the tape's long axis (I hope this is clear). You can do this if you are so inclined. Before you adjust azimith, a test for this would be to record and then play back a tape on this machine - regardless of how far off the azimith adjustment is, the recording should sound good (at least as good as one can expect from the linear audio) track. See the chapter: "Tape Path Alignment and Backtension Adjustment". 3. The audio head (and other parts) needs to be demagnetized - use an audio tape head demagnetizer. Stay away from the video heads. Some demagnetizers are powerful enough to damage them. Make sure the demagnetizer you use has a no sharp ends to damage anything - cover with electrical tape if in doubt. Turn on the demagnetizer and move it slowly near all metallic parts that the tape contacts - guides, levers, erase and audio/control head. As mentioned, do not go near the video heads. See the section: "Head demagnetizing". 4. The audio head is worn. If the poor sounds quality really bugs you, these can be easily replaced but they are not cheap since generic replacements are rarely available. Alignment will then be needed. 5. Tape path problem causing bad tape-head contact. See chapter: "Tape Path Alignment and Backtension Adjustment". 6. Your expectations for audio quality on the linear audio tracks on a non-HiFi VCR are unrealistic. The worst will be a stereo VCR in EP mode since the stereo tracks are less than half as wide as non-stereo tracks. Best will be SP non-stereo but even this is very poor for music. Once you get used to HiFi quality, linear audio sounds like crud.
Perform the following 'screwdriver and short tests' to narrow down a one-channel low audio problem: * While the VCR is playing a tape, CAREFULLY touch the tip of a screwdriver (or other metal tool) to each of the pins on the A/C head - you should be able to locate the L and R channels by the buzz resulting from signal pickup from the screwdriver. If the bad channel doesn't respond at about the same level as the good one, there is probably an electronics problem, not A/C head alignment. * If you can locate the signal ground for the A/C head, CAREFULLY short the output pin of the bad channel head to ground - the hum/buzz/whatever should disappear if there is a head or alignment problem.
While general quality of VHS linear audio is almost always mediocre, there should not be excessive flutter - wavering in pitch. Certainly it should not be noticeable for speech. How bad music sounds will depend on your expectations as well. Here are some possible causes: * Dirty/gummed up stationary guides or A/C head. * Lack of lubrication of the capstan or roller guides. * Excessively tight idler or other clutch. * Bad capstan motor, especially if direct drive type, or motor driver. * Bad pinch roller/bearing. Sometimes aftermarket replacements may be inferior and result in the same or worse behavior. However, usually they are fine. * Video head drum (upper cylinder) which is mounted off-center or which has excessive runout or wobble. This would most likely show up after the video heads are replaced. Sometimes, this may be detected by resting a dry finger very gently against the rotating drum - there should be NO detectable vibration. * Servo system problems. * Power supply problems. * 'Stiction' between tape and lower cylinder. * Unrealistic expectations of linear audio quality. Some VCRs are downright terrible, especially at EP speed. This is normal.
Sound is fine on pre-recorded tapes or tapes recorded on this VCR prior to the problem developing. New recordings have no sound whatsoever. Make sure your tape isn't bad. Yes, I know, this is unlikely, but very old tapes tend to lose oxide along the edges and guess where the audio goes. If the previous audio is erased but you now have silence, the problem could be that erase is working but no new audio is being recorded on the tape. First, check any audio mode or dubbing switches for proper settings. If you are using the RF input, see if the same problem exists with the RCA inputs. Sometimes, dirt/bad connections on the RCA inputs will trick the VCR into thinking you really want to use those instead of the RF. Pushing an RCA plug in and out a few times may clean these off. (From: Raymond Carlsen (rrcc@u.washington.edu)). I first saw this problem in Wards (Sharp) VCRs, then later in some Samsungs. The real problem is a bit of resistance in the connector on the full erase head. The FE head arm swings back and forth when loading and unloading the tape, causing the connections to weaken. That bit of resistance cause the bias/erase oscillator to fail to start up in record mode. If allowed to run that way, it can burn up that transistor and other components on the audio board. Just replacing the bad parts will not fix it for long. Cut off the plug and direct-solder the full erase head wires directly to the head. End of problem. Done a bunch of 'em.
Tapes play fine but audio is missing to the TV and when making recordings using the VCR's tuner. How is the TV connected? Through the RF/antenna input? If through the RCA jacks, of course, it could be a TV/cable problem. Bypass the VCR and check. For the RF, this could be many things: 1. There may be an incorrect source select or dubbing mode setting or a dirty set of contacts on a related switch. Check your instruction manual and cycle and/or clean the contacts of any suspect switches. Unplug the VCR for a few minutes to reset the controller - it may be in a weird mode. 2. Dirty contacts on the RCA audio in jack - some automatically assume you want to record from there if anything is plugged in. (Or, you may have left your CD plugged into the jack several months ago when you last used it!) Usually, inserting an RCA plug into the jack a couple of times will clean the contacts at least well enough to confirm that this is the problem. 3. Bad cable or bad connections inside the VCR. There is often a separate cable for audio (and video) between the tuner and the mainboard - reseat and/or test it. 4. Electronic fault resulting in not selecting the audio. This will require a schematic.
If the old audio track is unchanged - you get the new video but old audio, check that any dubbing switches are set correctly - to enable audio. If you are getting a mixture of old and new audio, then there could be a problem with the audio erase head (part of the A/C head stack) or its circuitry. Clean the audio/control head (the stationary head to the right of the video drum near where the tape re-enters the cassette. Check for dirt or tape oxide on or around the audio/control head. Beyond this, testing will probably require a schematic. However, if you can locate the connections to the audio erase head, use an ohmmeter to test for continuity of the coil. Check with an oscilloscope for the high frequency erase signal during record.
The VCR may be switching between HiFi and linear audio at random (with the HiFi light also flickering on and off or simply not selecting HiFi audio at all. This may be happening with only one audio channel (usually the right channel in this case). The sound out of a HiFi (not just stereo) VCR should be virtually indistinguishable from the original and for good quality source material, nearly as good as a CD. What to look for if it is really playing HiFi (try at slowest tape speed as this will have little effect on HiFi quality but will turn the linear track quality to crud). Use a tape with a musical recording for this: * Almost no tape hiss (background should be virtually silent). * Excellent frequency response (treble notes should sound natural). * Excellent dynamic range (loud louds and soft softs). * No detectable wow or flutter (no short or long term wavering in pitch). However, problems are possible: * Since the HiFi heads are on the rotating video head cylinder, they are subject to the same problems as video heads - and the same difficulties in diagnosing head problems. Dirt, damage, or electronic defects can cause the HiFi sound to be absent or distorted. A broken or badly worn HiFi head will simply cause the VCR to switch to the linear audio tracks. HiFi head alignment is more critical than video head alignment so this may need to be checked. Try adjusting the manual video tracking control as this will also affect HiFi audio tracking and see if this clear up the sound. * As with video heads, poor quality playback of self recorded tapes but fewer or no problems when playing pre-recorded tapes is one sign of worn heads. Like video, recording HiFi audio needs to use the heads twice. Thus, a slight loss in sensitivity or frequency response may still enable pre-recorded tapes to work reasonably well but will result in problems of playing back self-recorded tapes. Note that slight tape path misalignment would not affect self-recorded tapes anyhow but would result in poor playback of others - the opposite effect. * Old, worn, dirty, or bargain basement tapes will have many more dropouts than new name brand tapes. These will show up as noise, streaks, or dots in the picture *and* as pops or increased noise in the HiFi audio output. * It is possible that only one audio channel is affected. The audio may be missing, scratchy, distorted, or fading in and out. Where problems mainly affect one audio channel, it is usually the right one. One reason for this is that it is recorded at a higher carrier frequency (1.7 versus 1.3 Mhz for the left channel). Thus, problems are more likely to show up in the right channel due to either worn heads or a misaligned tape path. Since some of the audio processing is separate, electronics problems can easily affect one channel as well. * A whine, buzz, or hum in HiFi audio playback may indicate that the A/C head is too high - recording the control track on top of the ends of the video and HiFi tracks. However, other problems - particularly with tape interchangeability would almost certainly result. Note that A/C height doesn't change on its own - someone has likely been mucking with your adjustment screws (and who knows what else)! To confirm, record a couple minutes on a brand new or bulk erased tape. If the last 5 to 10 seconds of the recording is clear, the A/C head alignment is at fault since it is writing over the ends of the HiFi tracks 5 to 10 seconds *after* they are laid down and the end of the recorder will be unaffected. * A hum or buzz may be the result of problems in concealing the head switching point for the HiFi track. This could require an adjustment or be a failure or design flaw. See the section: "Hum or buzz in HiFi audio". * Electronic adjustments or faults in the HiFi audio circuitry could of course also result in record or playback problems.
Also see the chapters: "Video Heads and Upper Cylinders" and "Tape Path Alignment and Backtension Adjustment". (From: Jerry ()). The HiFi heads are more critical than the video heads. If they are warn down a bit, they can be very instable. Sometimes I can get a bit of a better response by increasing the tension arm tension a little. If you do this, you may have to touch up the guides. (From: Anthony Falvo (afalvo@borg.com)). I have had good luck making the HiFi tracking point meet the video head tracking point with slight adjustment of the 30 Hz switch point.
(From: Liam Keane (106350.3410@CompuServe.COM)). The noise you are hearing is FM audio track switching noise - from the changeover between the hi-fi audio heads on the head cylinder. The difference between video and audio switching noise is that the video noise can be shoved out of sight in the vertical blanking interval. The trouble with the audio is that our ears listen all the time! Some VCR's exhibit this worse than others. You can try adjusting the switching point to minimize it, but by the same token, some precorded tapes are particularly bad, with Disney tapes being about the worst I have ever heard.
Where a VCR has seen a lot of use, the video and HiFi audio heads are likely to be worn. However, evidence of video problems may or may not proceed HiFi audio degradation: (From: (Parker C. (parkerc@halcyon.com)). Your hifi audio is, technically speaking, not fluttering. The distortion you hear is the head switching noise becoming audible as the hifi heads are wearing out. On the outside chance you are not dealing with a worn out upper drum, you should first check the video envelope and confirm that your machine is mechanically adjusted correctly - i.e. check that the drum guides have not slipped. Hifi audio would typically become distorted if the tape path is not adjusted correctly. Audio playback level will not help the situation. Hifi Record levels almost never need to be adjusted, unless someone has been tweaking them in the field. (hint, hint). A note on record levels: occasionally we find that decreasing the video record levels on machines with poor hifi audio recordings will quiet things down for a little while. Did everyone get that? (decreases the video penetration into the hifi region of the tape).
Unusual noises from inside the VCR may be an indication of a problem or just a badly made cassette - try a different one. The most common cause for a squealing noise are tired weak belts that are slipping. Less likely is the need for lubrication. * A squeal when entering play or record mode - with the VCR perhaps aborting the operation - is usually caused by a slipping loading belt. * A squeal during fast FF or REW may indicate a slipping drive belt. * A squeal or whine during play or record (perhaps intermittently when the video head drum is spinning) could be a worn video head drum bearing or dirty or improperly positioned static brush (see also: "High pitched whine from inside VCR"). See the appropriate sections on cleaning, rubber parts, and lubrication. * A whine or buzz from the audio during playback of tapes not recorded on this VCR may indicate a grossly misadjusted A/C head - the linear audio heads are picking up the ends of the video tracks due to the A/C head being too low. Note that A/C height doesn't change on its own - someone has likely been mucking with your adjustment screws (and who knows what else)! * A whine from the audio (of the TV) while using the VCR may indicate bad grounding of the internal shields, other bad connections, or electronic problems.
Your first thought is probably of an expensive repair to a motor bearing or replacement lower cylinder. If there is a high pitched whine coming from inside the VCR when in PLAY, REC, or other mode which spins the video heads, you may simply have a dirty or improperly positioned antistatic brush. There is usually a metal strip with a carbon contact pressing against the center of the video drum spindle either above or below the deck. In rare instances, the bursh may be BETWEEN the upper and lower cylinders requiring more disassembly. It is very common for it to vibrate is just the right way to sound like a cat being strangled. Gently press on this strip or lift it off of the spindle while you hear the sound. If the whine disappears, cleaning and slight repositioning of the strip should be all you need to do. Do not remove this strip - it is needed to ground the rotating drum to prevent static buildup and video noise problems (see the section: "Firing (static) lines in picture during playback".
"Have recorded tapes with a Mitsubishi U52 that play back in English on same, but play back in Spanish with some other VCR's. What's up?" (Portions from: David R Mulligan (skipper@interlog.com)). It sounds like you are recording the SAP audio channel on the mono audio track, but normal on the HI-FI track. This would indicate that your television station broadcasts a Spanish dub over the SAP channel for those who prefer that language. Check the position of the audio playback source select. Also, any problem with the HiFi record or playback would also result in the VCR defaulting back to linear track playback.
There are two typical situations: * Playback is always in B/W. * Record is B/W but playback has normal color. If you can play pre-recorded tapes in color but tapes recorded on this VCR do not play back in color, there may be several possible causes. The simplest is that your input signal is too weak - a misadjusted antenna or cable with a large number of splitters - and the VCR's color killer thinks there is no color. Sometimes the threshold for detecting the color signal is set higher on the VCR than the TV which you are using to monitor the recording. Some questions: * Is the color TV's fine tuning set correctly? * Does it play pre-recorded tapes in color? * Does the tuner output produce color? * Does the video output work in color? * Is the problem the same for all recording speeds? * Do the tapes you record on this VCR play in color on another one? If the answer to all but the last question is 'yes', then the problem is most likely in the video/chroma circuitry associated with recording function. It could be as simple as the color killer setting being too low. Possible sources of problems with color recording: 1. Weak signal - check and/or adjust antenna. 2. Color Killer set to low. 3. Problems in tuner - does the video output work in color from the tuner? 4. Problems in chroma circuits. 5. Sometimes, marginal heads - less likely if it plays in color. If recording works fine as indicated by tapes made on this VCR playing fine on another one but pre-recorded tapes do not play back in color and the VCR works fine in all other respects there could be several possible causes: 1. Weak chroma signal level from VCR. 2. Color Killer set to low on TV. 3. Problems in chroma circuits. 4. Marginal or dirty video heads. Note that in all cases of missing color, checking with another TV and/or adjusting the TV's controls should be tried first as slight differences in signal levels between tuner and playback may cause a TV with marginal settings (fine tuning, color killer, chroma circuits) to switch unexpectedly between color and B/W.
First determine whether there is a problem with broadcast or cable, playing tapes, or both. If it is only broadcast or cable, then your source may be at fault. If it is fine with the VCR off but noisy when using its tuner, the problem could be in the tuner itself. Verify that the direct video output (RCA jacks) works properly with a pre-recorded tape. If this is noisy as well, then there are problems with the video circuitry or video heads. If there are problems with the Channel 3/4 output but the direct video outputs are fine, then suspect a weak or dead RF modulator. This is a little metal metal box with the Antenna In and TV Out connectors. It has circuitry which switches between the VCR's internal video signal and the antenna input. It also converts the video baseband signal to the channel 3/4 output required by the TV. Before you conclude that the RF modulator is to blame, check that the channel and fine tuning of the TV are properly set and that there are no other problems with the TV. Test the VCR with another TV. It could be that the signal from the VCR is just a little weaker than it is used to be. Try moving the channel 3/4 switch back an forth - it may have developed a bad contact. Try the other channel (3 or 4) - it may work better. Try moving the VCR away from the TV - sometimes interference from the TV will degrade the video quality. If you do conclude that the RF modulator is at fault, generic replacements are available from the parts sources listed near the end of this document or other electronics distributors for less than $25. Replacement is straightforward since there are only a couple of soldered connections but getting to the unit physically is sometimes a challenge.
Are you sure that the input signal is making to the VCR? Does the pass- through connection work? Double check the connections. Connect the cable you have on the ANTENNA IN of the VCR directly to the TV. Make sure it's center pin is not bent over or broken off. Try a new cable. Is the tuning mode switch (broadcast, CATV, etc.) set correctly on the VCR? If the signal is preset into the VCR, there still may be a bad connection inside preventing it from making it to the VCR's tuner. Sometimes, there are RCA style plugs inside that work loose. Otherwise, the tuner of the VCR is not working. This could be because it is broken or power to it is bad or missing. If all other functions of the VCR are working, it is likely (though not guaranteed) that the power supply is fine. There could be bad connections or dirty connectors as well. Beyond probing for bad connections and verifying your antenna hookup, there is not much that can be done without a service manual and test equipment.
This may be due to the proximity of the VCR to a TV or other component, outside interference, or a fault in the VCR. Determine if it in the video signal or is it only present when the VCR is close to or sitting on/under the TV? If so: * Have you rearranged your setup recently? It is common for TVs and VCRs to interfere with each other's operation. Your only easy fix may be to shuffle the components in your entertainment center. One simple test to see if it is the TV doing the interfering is to record a program partially with the TV off and then with it on - without changing anything else. If the quality of the recording is noticeably worse with the TV on, you know what is at least partly to blame. It is probably interference from the TV's switching power supply, deflection, or other circuits getting into the low level video circuits of the VCR. Either the TV or VCR or both are inadequately shielded. Hey, but the makers saved a few cents! Is probably isn't the cables but see if moving them around changes anything. If it does, then better (shielded) cables might help. It might be worth trying a position a grounded copper sheet between the TV and the VCR. I don't know how much if at all it will help. Does it happen when watching from the antenna/cable or only when a tape is playing or recording? * Interference patterns on cable may indicate a problem with the cable company or the hookup. It may even be system wide and under investigation - such temporary service problems are not uncommon. * If you are using one or more splitters to distribute the signal to multiple locations, be aware that each one introduces some signal loss and eventually this results in noticeable degradation making the system more susceptible to even low level interference which might otherwise be undetected. * Interference patterns while using the antenna may indicate just generally poor reception. Try repositioning the rabbit ears or outside antenna (if you have that option. Also check the connections and wiring - all the twisting and maneuvering can break or damage antenna cabling. If you live in an apartment complex - especially newer building of steel or steel reinforced concrete construction - reception may be inherently dreadful. Many of these offer a rooftop antenna feed or cable and for good reason. Try relocating the equipment - sometimes a different part of the room will have fewer problems. * Interference patterns only on recorded tapes that was not there in the original program may indicate a problem in the record circuitry of the VCR or interference from the TV (only if on). * Interference patterns only on playback of tapes regardless of where they were recorded may indicate a problem in the playback circuitry of the VCR or interference from the TV. Did this just start suddenly without you changing *anything*?? Does it now happen at all times of day? * If it does not happen all the time, try to determine what is common about when it does occur. Consider other sources of interference - local ham radio operators or other transmitters, light dimmers, compact or other fluorescent lamps, vacuum cleaner - even your microwave oven. Although less likely, it may be a neighbor's appliance doing the interfering. * To eliminate the VCR as the source of the problem, you may need to take it on a field trip to a friend or relative in a different neighborhood. If the patterns are still the same, it is probably a fault in the VCR and not outside interference.
These may be described as static or short bright or dark lines in the picture. They usually have a sharp start and may trail off or stop abruptly. They may be occasional (once every few seconds) or frequent (multiple instances per video frame). Also see the section: "Are your video heads really bad?" video head problems as large quantities of firing lines may be due to dirty, worn, or defective video heads. First, try a different tape - preferably a new recording made on a different VCR or a new commercial video. It is possible that these streaks are simply due to dropouts on the tape - missing bits of oxide or dirt causing momentary loss of video signal. Old, worn, or cheap off-brand tapes are particularly prone to dropouts. One characteristic of dropouts is that they may span video lines as well as video frames. If your lines are very short and random, they may be caused by a dirty, missing, or improperly positioned video drum static brush. In most VCRs, you will see a metal strip with a carbon contact pressing against the center of the video drum spindle either above or below the deck (or in rare instances, BETWEEN the upper and lower cylinders). The brush is there to provide electrical contact between the rotating video drum and the stationary lower cylinder and chassis. This is necessary since the bearings on which the upper cylinder rotate may not provide adequate contact and any static buildup caused by the spinning head cylinder rubbing against the tape may discharge through the bearings resulting in these firing lines. Carefully remove the static brush and clean the end of the spindle and carbon contact. This may be all you need to do to remove the static lines from your picture.
Most VCR problems will be limited to a specific subsystem - video, audio, tuner, servo, control. When multiple seemingly unrelated problems occur at the same time, suspect a power supply problem since multiple systems may be fed from common power supply outputs. There are always several different voltages used within a VCR - if one of these dies, some subsystems will work but will not receive the proper signals from the dead parts. So, nearly any kind of behavior is possible. Therefore, the first test is to determine, if possible, that the power supply outputs voltages are correct - both with power off and power on.
Power supply problems can range from intermittent behavior due to slightly out of tolerance voltages, hum, or noise to a totally dead VCR. Multiple system failures can result if one or more of the half dozen or so voltages used within the VCR are incorrect or missing. Some power supply problems are caused by power surges. These may result in a totally dead VCR or in overstress and subsequent failure of various components. A power strip with a circuit breaker, even with surge protector is not a reliable protection against power surges especially during lightning storms. The only sure protection is unplugging electronic equipment during storms - but then, what would your insurance agent have to do?
A variety of protective devices are used in VCRs. Of course, where the VCR is stone dead, check for a blown line or secondary fuse in the power supply. Occasionally, a fuse will blow due to a power surge or for no good reason and a new fuse is all that is needed. However, this is usually not the case and a new fuse will blow immediately. There is a chance that additional damage may result - proceed cautiously. If the fuse element is vaporized - black or silver coating on the glass, a short in the power supply is likely. However, a violent surge on the power line can also result in such a symptom. Various subsystems of the VCR may be protected by individual fuses as well. Sometimes, one of these will blow resulting in a variety of multiple systems problems but not a totally dead VCR. Look for fuses on the mainboard as well as the power supply. IC Protectors (ICPs) may be present on a single chip or small subsection of a circuit. Most common types are miniature fast acting fuses. Typically, they come in a black TO92 or rectangular .1"x.3" plastic case with two leads. Test these like a fuse - an IC protector should be a short if good. In some cases you may find a PTC (Positive Temperature Coefficient resistor - resistance increase dramatically due to excessive current heating the element) type of fuse or IC protector - these are self resetting once the overload has been removed. However, this also means that testing with power off will show low resistance even if a fault still exists (unless you test immediately). Measuring voltage across such a device with power on is one way of identifying a problem. One common form of this device appears as a little metal metal sandwich - the two plates are separated by the active material.
Reread Safety info before tackling any power supply problem in a VCR! VCRs typically use one of four types of power supplies (There are no doubt others): 1. Power transformer with linear regulator using 78/79XX parts or discrete components. The power transformer will be large and very near the AC line cord. 2. Power transformer with hybrid regulator like STK5481 or any of its cousins - multioutput with some outputs switched by power on. If it has one of these, check ECG, SK, or NTE, or post to sci.electronics.repair and someone can probably provide the pinout. Again, the power transformer will be large and very near the AC line cord. 3. Small switching power supply. Most common problems: shorted semiconductors, bad capacitors, open fusable resistors. In this case there is usually no large power transformer near the line input but a smaller transformer in a more central location. 4. Combo of the previous - these are less common. An input power transformer may supply low voltage to a switcher. 5. Camcorders and portable video camera-VCR combos include a battery charger and run all normal VCR (and camera) functions off of the battery. The required voltages are derived using DC-DC inverters. Here are some general comments for each type: 1. Troubleshooting is quite straightforward as the components are readily identified and it is easy to trace through from the power transformer, bridge or centertapped full wave rectifiers, regulators, caps, etc. The circuitry is not usually complex and the most common failures tend to be quite obvious. It should be possible to determine the correct output voltages from basic circuit principles. 2. Failures of one or more of the outputs of these hybrid regulator blocks are very common. Use ECG/STK/NTE cross reference to identify the correct output voltages. Test with power switch in both positions. Any significant discrepancy indicates a likely problem. While an excessive load dragging down a voltage is possible, the regulator is the first suspect. See: "VCR Power Supply Regulators" for pinouts of some of the common ones. The correct output voltages will be specified by on the regulator pinout. Replacement cost is usually under $10. 3. Switching supply problems are tougher to diagnose but it is usually possible without service literature by tracing the circuit and checking for bad semiconductors with an ohmmeter. Common problems - dried up capacitors, shorted semiconductors, and bad solder joints. In a supply that is dead - has blown the main fuse - check **all** semiconductors, capacitors, and resistors as a failure in one may damage others and just replacing the first one you find that is bad may result in it just blowing immediately. Fusable (flameproof) resistors (blue or brown body or boxy ceramic power type) may open up if there was a shorted switching transistor. Power resistors supplying current for the startup circuit may open from age. See the document: "Notes on the Troubleshooting and Repair of Small Switchmode Power Supplies" for more detailed information. Correct output voltages can be determined with some work - tracing the circuit. However, it is usually safe to assume that there should be at least one around 5 to 6 V for the logic and one or more others at 12 V or higher for the motors and other electronics. 4. Problems in either the power transformer/rectifier/filter capacitor section (usually no regulator) or switching supply are possible. However, they can pretty much be dealt with independently. Note: the switching supplies used in these usually run off of a lower voltage input than the more common off-line non-isolated type making them somewhat less hazardous to your health to work on. 5. Problems can occur in either the battery charger or power supply section. Short running time on battery alone is usually caused by a bad battery. If possible, try a known good battery or battery eliminator first to determine which it is. The older style portable units were quite reliable and easy to service. However, modern camcorders are so jam packed with microminiature surface mount unmarked circuitry that troubleshooting and repair is definitely not fun. Not to mention the joys of just getting inside with only a finite use of expletives. Don't overlook the possibility of bad solder connections as well.
Power surges or nearby lightning strikes can destroy electronic equipment. However, most of the time, damage is minimal or at least easily repaired. With a direct hit, you may not recognize what is left of it! Ideally, electronic equipment should be unplugged (both AC line and phone line!) during electrical storms if possible. Modern TVs, VCRs, microwave ovens, and even stereo equipment is particularly susceptible to lightning and surge damage because some parts of the circuitry are always alive and therefore have a connection to the AC line. Telephones, modems, and faxes are directly connected to the phone lines. Better designs include filtering and surge suppression components built in. With a near-miss, the only thing that may happen is for the internal fuse to blow or for the microcontroller to go bonkers and just require power cycling. There is no possible protection against a direct strike. Most VCRs have their own internal surge protection devices like MOVs (Metal Oxide Varistors) after the fuse. So it is possible that all that is wrong is that the line fuse has blown. Remove the case (Unplug it first!) and start at the line cord. If you find a blown fuse, remove it and measure across the in-board side of fuse holder and the other (should be the neutral) side of the line. With the power switch off, this reading should be very high. With the switch on, it may be quite low if the VCR uses a large power transformer - a typical primary resistance is 15 to 30 ohms. Some VCRs may be outside this range but if the reading is extremely low, the power transformer could have a partially or totally shorted primary. If it is very high (greater than 1 K ohms), then the primary of the power transformer may be open or there may be blown thermal fuse under the insulation wrappings of the transformer windings. If the VCR has a switching power supply, see the document: "Notes on the Troubleshooting and Repair of Small Switchmode Power Supplies". If the resistance checks out, replace the fuse and try powering the unit. There will be 3 possibilities: 1. It will work fine, problem solved. 2. It will immediately blow the fuse. This means there is at least one component shorted - possibilities include an MOV, line filter capacitor, transformer primary. 3. It will not work properly or still appear dead. This could mean there are blown fuses or fusable resistors or other defective parts in the power supply or other circuitry. In this case further testing will be needed and at some point you may require the schematic.
Should you always use a surge suppressor outlet strip or line circuit? Sure, it shouldn't hurt. Just don't depend on these to provide protection under all circumstances. Some are better than others and the marketing blurb is at best of little help in making an informed selection. Product literature - unless it is backed up by testing from a reputable lab - is usually pretty useless and often confusing. Line filters can also be useful if power in you area is noisy or prone to spikes or dips. However, keep in mind that most well designed electronic equipment already includes both surge suppressors like MOVs as well as L-C line filters. More is not necessarily better but may move the point of failure to a readily accessible outlet strip rather than the innards of your equipment if damage occurs. It is still best to unplug everything if the air raid sirens go off or you see an elephant wearing thick glasses running through the neighborhood (or an impending lightning storm). Generally, the backup battery or supercap will retain the clock and programming information long enough to ride out a typical storm.
The front panel clock, counter, and function indicators on most VCRs use something called Vacuum Fluorescent Display (VFD) technology. The VFD uses a vacuum tube which includes a heated filament and multiple phosphor coated anodes in the shapes of the letters, words, and symbols. A positive voltage on selected anodes cause electrons to stream from the filament causing them to glow. * The filament is in the form of a few fine wires running across the entire face of the display. Typical voltage is 4 to 6 V AC or DC depending on design. It may be possible to see a faint glow from the filament in a darkened room but the front panel will probably need to be removed to do this since its plastic filter is likely to block much of the the orange light from the filament. * The voltage for an 'on' anode is generally between 20 and 30 V positive with respect to the filament. Problems with a dim or dead display can be due to a lack or fault with one of these power sources, the drive logic (system controller), or bad connections. With some VCRs, a special DC-DC converter is used to drive ONLY the display and this a common failure item. See the section: "Dead clock in Hitachi manufactured VCR". Where the display works but is dim, there can be several causes: * Some VCRs have a 'night mode' which dims the display after, say, 10:00 PM. Check that you don't have the clock AM and PM set incorrectly. There is usually a way to disable this 'feature'. * If the VCR has been used in a location where there are heavy smokers, whatever tar and nicotine somehow avoided getting trapped in their lungs may have been deposited on the front and rear surfaces of the plastic display window and on the front of the display tube. Remove the front panel and use alcohol and a soft cloth to thoroughly clean all these surfaces. * The VCR may have seen a long active life. Like CRTs and other vacuum tubes, cathode emission and/or phosphor brightness can degrade over time. There is nothing much that can be easily done to remedy this. * The filament or anode voltage may be low or faulty due to a bad connection, dried up electrolytic capacitor, or other power supply problem.
What could be the cause of the video dying on a VCR after it is playing for a couple of hour? Here are some questions: Do all modes 'go out' or just PLAY? Does it happen suddenly or just gradually worsens until it is total snow? Or, do you get the 'blue screen' if it has this function rather than snow? Does the tuner still work? Conversely, does PLAY work but not the tuner? Do other functions like FF and REW always work? How is the time it sits turned off related to how much on time you get? Have you verified that the TV is fine? Is it possible that the VCR is covered up/closed in/installed with inadequate ventilation? It could be a loose connection or bad component. The usual way to narrow down the possibilities is to use what is called 'cold spray' or 'circuit chiller' on the appropriate sections of the circuit board until you locate the component that is failing with when it gets hot. I once had a VCR that needed a little fan blowing on it to keep it happy - much easier solution than actually hunting down the fault. If play or record just stopped and the tape unloaded, it could also be a mechanical problem like a marginal idler tire, idler clutch, or worn belt.
These are the kinds of problems that put gray hairs on parts of your body you didn't think could grow hair (hey, maybe that is good). First confirm that the correct fuse type and value was used for this particular model and revision number. Of course, measurements of the supply current on the bench show a wide safety margin (i.e., 2:1). I don't suppose there was any mention of what was being done when it stopped working? While monitoring the current, try really exercising the FF and REW, switching between editing/tape movement modes, performing FF and REW to the end of tape stops, etc. These are where I would expect to see current spikes. It may be some peculiar combination of actions that results in a momentary jam or conflict. Unless of course it is just some cosmic connection that takes place every 3 months!
So your cat decided it was time to practice the long-jump and didn't quite pick a stable destination. Your VCR is on the floor, Tabby is in the basement, and what to do? Overall, VCRs are quite tough. However, falling in just the wrong way can do substantial and possibly not immediately visible damage. If you take it in for service, the estimate you get may make the national debt look like pocket change in comparison. Attempting to repair a VCR that has been dropped is a very uncertain challenge - and since time is money for a professional, spending an unknown amount of time on a single repair is very risky. There is no harm is getting an estimate (though many shops charge for just agreeing that what you are holding is a VCR!) This doesn't mean you should not tackle it yourself. There may be nothing wrong or very minor problems that can easily be remedied. First, unplug the VCR even if it looks fine. Until you do a thorough internal inspection, there is no telling what may have been knocked out of whack or broken. Electrical parts may be shorting due to a broken circuit board or one that has just popped free. Don't be tempted to power the VCR even if there are no obvious signs of damage - turning it on may blow something due to a shorting circuit board. Then, inspect the exterior for cracking, chipping, or dents. In addition to identifying cosmetic problems, this will help to locate possible areas to check for internal damage once the covers are removed. Next, remove the top and bottom covers and front panel. Check for mechanical problems like a bent or deformed cassette basket, broken or cracked plastic parts, and anything that may have shifted position or jumped from its mountings. Carefully straighten any bent metal parts. Replace parts that were knocked loose, glue and possibly reinforce cracked or broken plastic. Plastics, in particular, are troublesome because most glues - even plastic cement - do not work very well. Using a splint (medical term) or sistering (construction term) to reinforce a broken plastic part is often a good idea. Use multiple layers of Duco Cement or clear windshield sealer and screws (sheetmetal or machine screws may be best depending on the thickness and type of plastic). Wood glue and Epoxy do not work well on plastic. Some brands of superglue, PVC pipe cement, or plastic hobby cement may work depending on the type of plastic. Cycle the cassette loading and tape loading mechanism manually by turning the appropriate motor shaft, if possible. Check for free movement of the various parts of the tape transport. Inspect for any broken electronic components - these will need to be replaced. If the fluorescent panel is broken, you can run the VCR without it but of course will not be able to see any front panel displays. Check for blown fuses - the initial impact may have shorted something which then blew a fuse. There is always a slight risk that the initial impact has already fried electronic parts as a result of a momentary short or from broken circuit traces and there will still be problems even after repairing the visible damage and/or replacing the broken components. Examine the circuit boards for any visible breaks or cracks. These will be especially likely at the corners where the stress may have been greatest. If you find **any** cracks, no matter how small in the circuit board, you will need to carefully inspect to determine if any circuit traces run across these cracks. If they do, then there are certainly breaks in the circuitry which will need to be repaired. Circuit boards in VCRs are never more than two layers so repair is possible but if any substantial number of traces are broken, it will take a great deal of painstaking work to jumper across these traces with fine wire - you cannot just run over them with solder as this will not last. Use a fine tipped low wattage soldering iron under a magnifying lens and run #28-30 gauge insulated wires between convenient endpoints - these don't need to be directly on either side of the break. Double check each connection after soldering for correct wiring and that there are no shorts before proceeding to the next. If the circuit board is beyond hope or you do not feel you would be able to repair it in finite time, replacements may be available but their cost is likely to be more than the VCR is worth. Locating a junk VCR of the same model to cannibalize for parts may be a more realistic option. Once all visible damage has been repaired and broken parts have been replaced, power the VCR up and see what happens. Be prepared to pull the plug if there are serious problems (billowing smoke would qualify). Determine if it appears to initialize correctly - without shutting down. Play a garbage tape to determine if there are any problems that might damage the tape. Watch and listen carefully for any evidence of poor tracking, video noise, tape speed instability, or weak or muddy audio that might indicate that tape path alignment requires further attention. Listen as well for any unexpected mechanical sounds that were not there before. Very likely, the VCR will be fine, you can replace the covers, and now find a more secure spot for it to prevent this sort of event in the future. Use your own judgment with respect to the cat.
Someone took your camcorder to the beach this summer and now it has sand or perhaps salt inside. Or, that cup of tea on top of the VCR wasn't as stable as you thought. Now, it behaves, well, strangely. Can this possibly be fixed? Will it be worth the effort or expense? Unless this is a really sophisticated (i.e., costly) unit, I doubt whether it will pay you to take it anywhere for repair. Even if it is successfully repaired, its reliability may be questionable. Furthermore, as with equipment that has been dropped or physically abused, few repair shops will be inclined to touch the job. They really don't like challenges of this sort. That leaves you! If anything got wet with saltwater and it has been just sitting, you can probably forget it. Without immediate attention (and I mean immediate, not later, not tomorrow, NOW!), saltwater corrosion can set in very quickly and attacks electronic components, circuit board traces, cable wiring, and mechanical parts. The only thing worse might be a peanut-butter-and-jelly sandwich 'played' in your VCR. On second thought, that probably would not be all that bad. Although it is probably too late, the first thing to do when electronic equipment gets wet is to remove the power source - pull the plug or remove the batteries. Don't be tempted to apply power until you have determined that everything is completely dried out inside and out. DO NOT use strong solvents anywhere! These may attack various plastic parts or cause internal damage to electronic components. The following was written assuming sand, salt, and liquid contamination everywhere! Modify based on your specific situation. Mechanical intensive care: 1. Disassemble as much as possible - sand and surf (or other liquids) find their way into the tiniest nooks and crannies. You need to get it all. 2. Make a drawing of the belt routing, remove the belt(s), wash and dry them, label and set them aside. 3. Use a soft brush (like a paintbrush) to dust out as much sand as possible. Hopefully, you can get it all this way. A vacuum cleaner with a wand attachment may prove handy to suck out sand. Sand will tend to collect on lubrication, especially grease, which will need to be completely cleaned out and replaced. Don't use high pressure compressed air, you will just spread it around. Any grease or oil on which sand has collected will need to be totally removed and replace with fresh lubrication. 4. If there is evidence of salt (remember, I said forget it...but), you will need to wash it off. Yes, wash it. Keep water out of the motors. Use low pressure compressed air (a blow dryer on low heat should be fine) to dry so that it does not rust. Ditto if it is still wet with contaminated liquid (we won't say where this came from), wash with fresh water to remove all traces of it as quickly as possible. Then dry completely. Depending on the situation, a final rinse with 91% or pure isopropyl alcohol may be desirable to decrease drying time. This should be safe for most mechanical assemblies. Degreaser may be used if it is safe for plastic and rubber parts. Lubricate all bearing points with a drop of light machine oil - electric motor oil, sewing machine oil, etc. (Never never never WD40). Lubricate gears, cams, and sliding parts with a light plastic safe grease such as Molylube. Parts like the idler clutch may need to be disassembled to get at the friction felt. Other mechanical parts like cam gears may need to be removed to be properly cleaned. Don't mess up the timing relationships when you do this! 5. Reinstall the belts and reassemble in reverse order. Electronic intensive care: 1. Remove the circuit boards and label the connectors if there is any possibility of getting them mixed up. If the circuit board(s) are soldered to the rest of the equipment, then you will have to improvise and work in-place. 2. Wash with water and dry thoroughly. This does work. I use it routinely for degunking remote controls and rubber membrane keypads, for example. I have heard of people cleaning contaminated computer keyboards in their dishwasher! The important objective should be to get corrosive liquids off the components and circuit traces as quickly and completely as possible. A final rinse with 91% or pure isopropyl alcohol will decrease drying time. However, there is a slight risk of damage to sensitive electronic components should some be trapped inside. Pat dry, then use warm air from a hair dryer (or heat gun on low) to completely dry everything. Moisture will be trapped in controls, coils, selector switches, relays, transformer cores, connectors, and under large components like ICs. DO NOT operate until everything inside and out is thoroughly dry. 3. Use spray contact cleaner on the switches and control cleaner on the control and adjustment pots. DON'T turn the internal adjustments without precisely marking the original position - else realignment will then be needed. However, exercise the user controls to help the cleaning process. Note: drying time may be quite long. For parts with inaccessible areas like membrane keypads, you may need to wait a week before normal operation is restored. Be patient! Once everything is completely dry as a bone and reassembled, power it up but be prepared to pull the plug or pop the batteries if there are serious problems See if the display comes alive and the transport appears to initialize. Attempt to play a garbage tape to determine if there are any mechanical problems that might damage the tape. Look and listen for any abnormalities which may require additional attention. Then address specific problem areas. Also see the section: "VCR was dropped" for additional info. Obviously, this description is very simplistic. The important thing is to get every last grain of sand, salt, and other contaminants off of the mechanisms and circuit boards quickly. As noted above, moisture may collect inside certain electronic parts and it is essential that these be dried completely before attempting to apply power to the unit. If you do not, at best it will not work properly and you may do additional serious damage due to short circuits. For the mechanics, the same applies though this is trickier since certain parts need to be lubricated and these may not be readily accessible or obvious. Don't be tempted to overdo the lubrication - too much is worse than too little. For camcorders, some parts of the optics or enclosed DC-DC converters may be impossible to access and clean of scum.
See the document: "Notes on the Troubleshooting and Repair of IR Remote Controls" for extensive information as well as links to the web sites of manufacturers of universal remote controls - these include setup info.
So you just pulled your favorite tape from the VCR and there are two tape ends dangling from it. Or, perhaps, your VCR has just munched on that tape and a section is now seriously crinkled. Maybe you haven't been following the recommendations on preventive maintenance; maybe your VCR was just hungry. In any case, what to do? The recording is, of course, irreplaceable. Despite this, I recommend you chuck it. An imperfect splice or seriously crinkled section of tape can shatter your video heads - the most expensive single part in a VCR. If it is something you really treasure, than what I would do is the following: Note: If you have never seen the inside of a video cassette, try the following on a couple you really don't care about first so that if you screw up, there is no great loss. Too bad AOL doesn't send out Internet software on video cassettes, huh? CAUTION: The video tape itself is really really thin and easily crinkled. Be very gentle when handling it and avoid touching the oxide (dull side) if at all possible. 1. Locate a garbage cassette and disassemble it. Throw away the tape but save everything else including the reels. See the section: "Disassembling a VHS cassette". 2. Construct two cassettes from the combined collection of parts you now have. Cut out any sections of tape that got mangled. Cassette 1 has the first section of tape (before the break) and uses one empty reel from the garbage cassette for the supply reel. Rewind this to the beginning. Cassette 2 has the second section of tape (after the break) and uses the other empty reel from the garbage cassette for the takeup reel. Use the little plastic plugs that came from the garbage tape reels or some adhesive tape to connect the tape to the reels. 3. If the break is at one end, you can just reconnect the bulk of the tape to the reel and dispose of the original leader. Just don't rewind or fast forward all the way to the end as the automatic end sensor will not work (for the particular end that has been repaired). What will happen is that instead of the sensor stopping REW or FF (as appropriate), the tape will run to the end and the VCR will then shut down when it discovers that the tape isn't moving. This can put additional stress on mechanical parts and/or rip the tape from the reel. Serious damage to the VCR isn't really that likely. 4. Copy to a good cassette. 5. Dispose of the original(s) or clearly mark 'DO NOT USE' with a detailed explanation.' Filip (I'll buy a vowel) Gieszczykiewicz (filipg@repairfaq.org) is a little more definitive about this: "I find the destruction of it more fulfilling :-) ... put it in a paper bag and smash the life out of it with a big, heavy hammer - or a small ball hammer for an even higher satistfaction ratio :-) " The idea is to never have a splice in a VHS cassette. (Even a seriously crinkled tape such as might result from a tape eating incident can damage the heads.) It is possible to splice safely but as noted, it can be quite costly if you don't get it quite right.
These instructions should enable you to get inside a cassette for the purpose of reattaching a leader that pulled off of one of the reels or to enable you to transfer its contents or a portion thereof to another shell or vice-versa. 1. Peel off the label on the side or carefully slice down its center line with a knife or razor blade. This is necessary to allow the cassette halves to be separated. 2. Place the cassette upside-down and remove the five (5) phillips head screws and set aside. 3. While holding the cassette together, place it label side up on a clean surface. 4. Gently remove the top (along with the hinged door) to reveal the interior. At this point, you should see something that looks like VHS Cassette - Inside Top View. When you reassemble the cassette, take care to avoid crunching the tape under the hinged door - depress the unlock button on the side and lift it clear if needed.
Cassette rewinders typically consist of a low voltage motor powered from a built in transformer or wall adapter, a belt, a couple of reels, and some means of stopping the motor and popping the lid when the tape is fully rewound. Note that some designs are very hard on cassettes - yanking at the tape since only increased tension is used to detect when the tape is at the end. These may eventually stretch the tape or rip it from the reel. As noted, I don't really care much for the use of tape rewinders as normal use of rewind and fast forward is not a major cause of VCR problems. Sluggish or aborted REW and FF may simply indicate an impending failure of the idler tire or idler clutch which should be addressed before the VCR gets really hungry and eats your most valuable and irreplaceable tape. Problems with tape rewinders are usually related to a broken or stretched belt or other broken parts. These units are built about as cheaply as possible so failures should not be at all surprising. The drive motor can suffer from any of the afflictions of similar inexpensive permanent magnet motors found in consumer electronic equipment. See the section: "Types of motors in VCRs". A broken belt is very common since increased belt (and tape) tension is used to switch the unit off (hopefully). Parts can pop off of their mountings. Flimsy plastic parts can break. Opening the case is usually the biggest challenge - screws or snaps may be used. Test the motor and its power supply, inspect for broken or dislocated parts, test the power switch, check and replace the belt if needed. That is about it.
"I've got one of the Damark ones and it does work for Macrovision protection, depending on the input deck. My 10 year old Panasonic VHS Hi-Fi (No MTS tuner, Dolby(tm) B linear stereo non-Hi-Fi audio too) works fine as an input deck, while my new JVC Hi-Fi doesn't. Why some input decks work and others don't is my question. Anyone know? Is there added circuitry that the newer decks have to defeat the stabilizer boxes?" (From: Jeroen H. Stessen (Jeroen.Stessen@ehv.ce.philips.com)). JVC owns the patent for VHS. JVC has made a deal with Macrovision that from a certain date in the past *no* VHS recorder licensed by JVC shall be able to record any video signal that contains Macrovision's copy protection pulses. Any video recorder from before that date (VHS or other) might well work OK on the altered video signal! The copy protection pulses upset the video AGC and H-sync. TV's usually don't have a video-AGC. Thus the whole idea of the Macrovision method is to disturb the video AGC that is inside every VCR - the manufacturers even *must* make the video AGC sensitive to those pulses! In the TV, the horizontal sync processing may be disturbed by the Macrovision pulses. Indirectly that also disturbs the DC clamping circuit. So you may see horizontal phase as well as brightness disturbances at the top of the picture. The stabilizer box removes the extra pulses and makes it into a normal video signal again. No VCR should ever know the difference, so they should all record properly again. At the same time, all TV's are required to ignore the copy protection pulses. As a TV-designer I can tell you that this is sometimes far from trivial. Not in the least because in the beginning we were not included in "the deal". There may be TV's around whose brightness and/or sync will be disturbed by the Macrovision pulses. Officially, this is the reason for existence of the stabilizer boxes: to view better, not to copy better. Unofficially, they are sold for copying, of course. Keep in mind that the Macrovision 'standard' (pardon me) has been improved several times. Old decoders may not be able to cope with newer tapes. In order for the decoder to key out the pulses in the vertical blanking interval, it must first synchronize properly itself. That process too may be disturbed (by extra pulses on newer tapes to older decoders). Those Macrovision a**holes are smarter than you think. Unfortunately, their signal may also disturb some TVs which are used legitimately. And then it becomes *our* problem too. The next step will be that digital-TV decoders will output an analog TV signal with Macrovision copy-protection pulses so that you may watch but not record your pay-per-view program. Same problem, same solution ... And I thought that PAL/Secam/NTSC were *standards*, sigh ...
(From: Mark T. O'Bryan (obryan@gumby.cc.wmich.edu)). Look at it this way. The reason that you see changes in brightness is that the "protection" signal that is added makes the unit's AGC (auto- matic gain control) think that the level has shifted, when it hasn't. So it adjusts to compensate. So if you have an older VCR without AGC (or a mild application), it may not be affected as much (or at all, after passing through a "stabilizer" box). If the sensitivity of the AGC is high (like it is on most JVC's) and the response-time is short, any small amount that leaks through will still cause problems. For those familiar with the electronic circuitry in VCRs, both the time constant in the RC circuit for response-speed, as well as the AGC sensitivity can be adjusted by manipulating simple resistor values. I don't have any specifics on this (and it varies on different machines), so don't bother asking for it :-). But at least you now know why some decks react differently.
"I've just started to use the closed caption feature of my TV and have a problem with pre-recorded video tapes, and am wondering if it could be the VCR. The problem is simple: about half the tapes I've watched displays the CC information incorrectly (many missing characters and/or lines), or will not display it at all. Sometimes I can improve the CC display by adjusting the VCR tracking to the point where the picture starts to become fuzzy, but for the most part it remains garbled and uncorrectable." Of course, as with so many other problems, poor quality or well worn tapes can result in erratic closed caption decoding. Therefore, I would not recommend diving into the bowels of your VCR before trying out some other tapes. (From: Thomas D. Kite (tom@olive.ece.utexas.edu)). Sounds to me like the head switching point is too far down the screen, i.e. the point at which the VCR switches between the video signals from the two heads is too late. You can check this if you have a TV with vertical hold. Set the hold to give a stationary or slowly rolling picture so that you can see the head switch, which will appear as a tearing of the picture. This should occur during the blanking period, but I suspect that your VCR is switching sometime later. If so, open it up and look for a preset on the main board labeled 'Head SW PT' or something like that. Twiddle it so that the tearing backs up the screen into the blanking part (again, do this while the picture is rolling slowly). Hopefully, this will mean your VCR has done its switching by the time it gets to Line 21, and the CC information will be intact. (From: Richard Beeler (vcrmonthly@earthlink.net)). This could be Copy Guard on tapes interfering with the closed caption decoding. We had one that was doing the same thing on some pre-recorded tapes and not others. We finally had to add a 'video stabilizer' between VCR and TV - that corrected the problem.
The clock display is dark but other functions are normal. Your VCR probably was made by Hitachi (Sears is one of several brands that may be manufactured by Hitachi). If so, probably your DC to DC converter went bad. Please note that the the converter is close to the front of the VCR and not on or near the main power supply board. Also check the IC protector (possibly ICPN5) as it may have blown. You should also replace the two 47 uF 50 V and the 100 uF 35 V capacitors near the DC to DC converter. These are known to go bad resulting in failure of the DC to DC converter. Complete repair kits are available from suppliers like MCM Electronics. These will include all components likely to have gone bad. For some models: (From: Sire Johnathan (sirejohn@bbs-la.com)). Behind the Channel selector is an upright PCB. on the upper inside corner find a 1/2" sq. transformer can with top hole and slotted core adjust. The schematic nomenclature is T101 or T102. Next to it, find a TO-220 power transistor. Replace the Pwr Xstr, filter caps in secondary side rectifier with DOUBLE the voltage ratings, and a small choke (L1?) that feeds primary power to the power transistor (fuses open). When working properly, current draw through primary circuit should be less than 200 mA.
You have a JVC VCR, 1990 or so vintage and it upped and died on you. JVC, huh? How did it die? What are the symptoms? Major tracking problems? Eats tapes? JVC VCRs of that era tend to shed parts in the tape loading mechanism - easily fixed. Unless it is a serious electronic problem (there is a minor one which results in similar symptoms - see below), a service manual may not help. And even then, it may not have the information you need. Check the roller guide assemblies (see the sections: "Parts of the tape transport in a VCR" and "General tape path alignment problems"). There are two types of failures that occur frequently on various JVC models: * If one of them flops around (they will be loose except in the fully loaded position but should not come off the track), then it has lost the brass guidepost underneath. Remove the bottom cover and you should see it drop out. Without the guidepost, the roller guide will not seat properly and tracking will be way off. Use a dab of Epoxy or superglue to replace the brass post fully against the shoulder in the cast roller guide base. Just popping it back in, even if the post appears snug, will result in a callback. If this is done carefully, tape path realignment should not be needed. Alternatively, replacement roller guide assemblies are available. WARNING: do not attempt to load a tape if a roller guide assembly can be lifted off of the track - it may smash the rotating video heads - very expensive lesson. Of course, it may already be too late :-(. * If a roller guide does not seat fully against the V-Stopper (the end piece) but the brass pin has not fallen off or loosened, then a linkage pin may have loosened. This is plastic pin which is the hinge for the linkage which moves the roller guide assembly. I have used a tiny screw from the top to firmly reattach this pin. Clearances are really tight so if the screw head sticks up more than a mm or so, it will restrict movement of the roller guide assembly resulting in loading and/or unloading problems. Alternatively, a dab of plastic cement may work. In either case, tape path realignment should not be needed. To get at the bottom of the roller guides or hinges, you will probably have to convince the VCR to start loading a tape and then pull the plug just as the mechanism is in a position where you can get to it. * Another common cause for a band of video noise at the top or bottom of screen on some JVC models: Defective capacitor (may be C6, 3.3 uF, 50 V) on drum motor resulting in bad PG pulse. It looks like a tantalum cap but a regular electrolytic should be satisfactory. Even Radio Shack will likely have a replacement. In some severe (or shall we say, strange) cases, good and bad/no video may occur randomly each time the VCR enters PLAY mode but will remain that way until the tape is unloaded. (From: Mark Shoberg (mewzaq@webtv.net)). When replacing the 3.3uf cap on the motor board (this is for the older bottom mounted types) just cut away the plastic piece covering it a little bit. This way you don't risk damaging the video heads and it is easier as well.
A number of Panasonic and other Matsushita brand clones use a switching power supply which has a couple of common failure modes. * Blown fuse and shorted switchmode transistor and possible other failed parts. Replacement of the obvious shorted or open parts usually cures these. Test all semiconductors and fusable resistors - do not assume that a single part is bad. If you just replace the first bad part you find, it may just be blown again by other bad parts. * Low output voltages. If the 5 V (approximately) outputs measure low, 3.5 V, for example, then there is a leaky capacitor in the power supply startup limiter. A common part number is C14 or C21 (depending on model) which is 1 uF, 50 V. * The primary and secondary side filter and other electrolytics may lose capacity resulting in hum or ripple and regulation problems. Replacing all electrolytic capacitors in the power supply is probably the best solution. Check out the schematic for a typical Panasonic switchmode power supply available at this site under "Various Schematics and Diagrams". Some of the sources listed in the section: "Suggested Parts Suppliers" sell power supply rebuild and capacitor kits. Unless your power supply is missing, one of these kits will probably fix it - and you need to know is how to solder!
Symptoms include anything from erratic behavior to acting totally dead. There are many RCA models for which the info below applies. (From: Ken Koskie (aw345@lafn.org)). This may be one of the RCA VCRs plagued with intermittent diodes. RCA recommends replacing the following diodes; D108, D109, D110, D112, D114, D1103 and D1104. Their part number for the diode kit is 201066. "I am currently working on a GE VCR Model VG-4016 with the following problem. When the tape is inserted it loads fine the head starts spinning but it doesn't play because the capstan is not turning. If you push play a second time it start to play but is in the X2 mode so its going to fast." (From: Frank Fendley (frank.fendley@datacom.iglou.com)). Common solution for this - replace D108, D109, and D110 - even if they test good with a meter. ECG125 works well for this (2.5A/1000PIV). While you are at it, also replace D105, D106, D111, D112, D113, D114, using the same replacement. Samsung must have purchased 40 billion bad diodes when they built these units. Funny thing is, they almost always test OK with a meter but replacing them fixes the problem. Apparently they go open under operating voltage, but not under the lower voltage provided by a meter. Alternate solution (fairly uncommon) - replace IC201. (From: Mark Z. (zmachar780@aol.com)). If this model is the type I think it is, there is an open diode along the inside edge (toward the mechanism rear) of the top circuit board. There is actually about 7 diodes which tend to go bad in these due to underrating. Five are in the area I mentioned, that is two along the edge at the middle of the board, and three further back, and two are located under the power transformer. Other problems, such as no display or no power, will occur if any of the others go bad. Suggest you replace them all; Any decent 1N4007 or such will do fine. Radio Shack has "2.5A 1KV" diodes which would be fine. For some RCA VCRs with somewhat similar symptoms: (From: TVman (tvman@newwave.net)). For the RCA VR321 which appears dead, clock display may come on after a few minutes, Q1 runs hot: Replace: C09 (22 uF, 16 V) non polarized capacitor in power supply.
Two words: Mode Switch. Whenever you have problems that seem to come and go or go away temporarily with repeated attempts to play or enter some other mode, the problem is very likely a dirty (or worn) mode switch (may be called the 'mechanical state switch' by some. The chassis of Sharp VCRs come in several flavors. Here is a description of two of them with respect to getting at the mode switch: * Newer models (e.g., VC-A607) have the mode switch as part of a modular loading motor assembly. This is found on the top in the far right corner of the transport. It is mounted by 3 screws, easily removed. There are no timing relationships to get messed up as long as you don't try to cycle the mechanism while disassembled. Therefore, it can be removed and replaced without concern for gear timing. The link between the mode switch and drive gear is keyed so it will go back together properly. To access the mode switch, unplug the connectors, remove the single belt that drives the eject mechanism, and remove the 3 screws. It should now be possible to detach the entire assembly. Underneath, you will see a disk with a keyed center hole - this is what must be replaced with the same orientation as it was before removal. The disk snaps off easily revealing the tracks and contacts of the mode switch. Thoroughly clean and slightly increase the spring pressure of the contacts. Replace in reverse order. Make sure the post slips into the keyed hole as you replace the assembly and double check that it is seated before tightening the screws. * Older models (e.g., VC7864U) are a bit trickier. The mode switch on these models is sandwiched between the loading gears and a mounting plate - all parts of what I will call the 'loading gear assembly' underneath the tape transport. To access the mode switch, this entire unit needs to be removed and partially disassembled. The gears operate the roller guide loading mechanism, and a couple of cam operated levers which are conveniently hidden when it is removed or reinstalled. It is driven by the loading motor via a couple of idler gears. Timing marks: There is at least one critical timing relationship that needs to be preserved when the loading gear assembly is removed. I recommend that you put your own timing marks on all gears before loosening the 3 screws that anchor this unit. You will need to unsolder 4 connections as well before it will come free. Once the bottom of this unit is accessible, the mode switch can be snapped apart and cleaned. I believe this is best done with the VCR in the unloaded and ejected state. However, there are still a couple of levers that will need to engage properly when the loading gear assembly is replaced. These press on internal cams that are hidden when everything is together. Much fun.
Symptoms are that upon eject, a loop of tape may be hanging out and possibly held by an arm inside the deck. The cause is gummed up lubrication on the pivot of that 'half loading arm' on the right side of the transport. It is supposed to help pull the tape out of the cassette during loading and then spring back when unloading. If the lubrication gets sticky, it does not spring back and grabs onto the tape during eject. Remove the half loading arm by unscrewing the locking nut. Count the revolutions of the nut as you do this since it sets the height which is somewhat critical. Clean the bearing and shaft and then lubricate it with a drop of light oil or a dab of light grease. If you forgot to count the turns or the nut had originally loosened up, just center its height within the range over which the tape moved stably past the first fixed guidepost and/or A/C head. Then confirm reliable loading and unloading with several different tapes. Try using forward and reverse search to assure that the tape isn't moving up or down on the guides. Make sure there is absolutely NO tape edge damage. Someone gave me a fancy Sony HiFi VCR with the request "I will pay up to $150 to fix it. Circuit City said that it could not be repaired for less than $250 because my kids had gotten into it and recommended replacement" (I wonder why). It was the stupid loading arm. Obviously, the grade-A techs at Circuit City were either under orders not to suggest repairs if they could get away with it and/or had never even taken the top off of the thing because the owner had mumbled something about his kids. I could have made a bundle off of that. I could have had a nice VCR for nothing. I just gave it back and told him about the bit of cleaning and drop of oil. (From: Sire Johnathan (sirejohn@bbs-la.com)). I recall well from counting turns until that elastic nut lifts off the stud is very repeatably 6.5 - 6.75 turns. Checking it with the Sony height specs is always within limits. Don't forget to check the smooth running of tape over this 1/2 load pre-threading guide pin in the reverse scan direction. The tape should maintain same height when changing rapidly between FWD SCAN and REV SCAN. A worn conical pinch roller can cause tape height shifting and tape edge-rippling or top-slacking because the pinch roller becomes the primary tape guide in REV SCAN. Changing quickly between REV SCAN & PLAY modes while monitoring normal linear audio treble and tracking can reveal any mis-skewing of the tape path as it 'returns into the groove' in PLAY mode. Sony pinch rollers are notoriously short-lived causing most tape edge-rippling and mistracking. BEWARE of 3rd party substitute parts as they are frequently out of tolerance and poor bearings necessary for Sony mechanisms.
(From: VCRMonthly (vcrmonthly@aol.com)).
Later Sony VCR's have "emergency" codes that show up in the Fluorescent
Display on certain failures. The code shows up in the "seconds" position
and they are as follows:
Code Problem
-----------------------------------------------
00 Normal.
01 Abnormal Take-up reel rotation.
02 Abnormal Supply reel rotation.
03 Abnormal drum (head) rotation.
04 Abnormal forward cam motor rotation.
05 Abnormal reverse cam motor rotation.
06 Abnormal cassette loading.
07 Abnormal cassette unloading.
Play a tape until the VCR shuts off and then check the failure code to help
diagnose the problem. These codes are cleared when AC is removed or when
another function button is pushed.
Some Sony VCRs may use the error coding summarized below:
(From: J-S Ferreira (Gal@microtec.net)).
Error Code Block Problem
--------------------------------------------------------------
00 No error
01 - 09 Control motor
(encoder) Unable to detect the position
10 Mechanism Loading not completed
11 (deck) Unloading not completed
12 " No eject
13 " End sensor fault (take-up side)
14 " End sensor fault (source side)
15 " Dew detected
20 Drum Drum motor won't rotate
21 " Drum servo not locked
30 Capstan Capstan motor won't rotate
31 " Speed not locked
40 Reel Take-up reel FG not locked
41 " Source reel FG not locked
42 " Measure abnormally ended (whatever this means)
A typical set of symptoms and questions: "The capstan motor on my Sony VCR has lost the war and is in need of replacement. Based on my Dejanews search on this topic, this is evidently not an uncommon occurrence :(. My local repair shop diagnosed the problem for $30 and gave me a $200 estimate to fix it. 3 questions: * Is this reasonable? * Does a capstan motor for this VCR really cost $95? * Given that I'm fairly handy with electronic repair, but inexperienced with VCR repair, is this something that I should attempt without a service manual? In other words, is this a particularly difficult or tricky repair? To satisfy the curious: the symptoms were a jittery picture on playback of tapes. The problem began with playback in EP mode only (the picture would freeze and hi-fi audio would "ratchet" as though the tape had come to a halt). It progressed until this started happening in SP mode as well. The problem got much worse the longer the unit was running (or the farther into a given tape I watched...)." (From: Bob Groger (BobG1@msn.com)). This is a common problem, but you don't need to replace the motor! Sony sell a new bearing assembly for about $25. There is a service bulletin out on this. The bearing housing bends after a period of time from pinch roller pressure. The new one is much stronger. Quick but temporary cure is to grasp the top of the bearing housing with big pliers and bend slightly towards pinch roller. This is NOT a guarantee! (From: ZMachar780 (zmachar780@aol.com)). They have a lot of bad capstan motors on these. The bearing collapses a little, then the flywheel scrapes on the drive coil. Sony sells a replacement bearing assembly which would save a few bucks over a cap motor, but frequently the capstan shaft is worn anyway and should be replaced. Sony will ID the part number(s) and sell you the part directly (on a credit card). Call them at 800-282-2848. (From: Willis Chung (nikonkidf3@aol.com)). This is the classic Sony capstan motor bearing problem. The capstan motor is a direct drive unit with a large flywheel/magnet assembly mounted just below a set of flat coils. The bearing that the capstan turns through is also part of the bracket that supports the motor. With time, the bearing wears out, allowing the capstan to tilt ever so slightly. This tilt causes the capstan flywheel to come into contact with the coils, causing a scraping sound, intermittent pauses, and eventually causing the motor electronics to die. Stop using the VCR now to prevent damage to the motor's electronics. The capstan motor bearing can be replaced without having to replace the entire motor. The bearing is available direct from Sony for about $12, but the entire motor costs about $45-$55. For the SLV-575, the part number for the bearing assembly is X-2625-269-1. However, replacements for other VCRs have different part numbers - best to check before ordering. Replacing the bearing is straightforward, and anyone can do it (well just about anyone!). 1. Remove top and bottom covers with machine unplugged 2. Unplug connector cable to capstan motor circuit board 3. Unscrew motor from chassis (3 screws accessed from top of chassis. 4. Remove capstan flywheel and shaft from motor (just pull to separate it from the rest of the motor) 5. Unscrew capstan bearing from motor assembly (3 screws) 6. Assembly is reverse of disassembly. 7. Play junk tape to see if there is any folding of the upper or lower edges of the tape, especially just past the capstan. You may need to make some adjustments to the metal guides to the right of the capstan. 8. Make comments to people around about cheap motors, using harsh language. The repair is easier to do than to explain! (From: David A. Sanders, II (capeone@aol.com)). The bearing part number for the Sony SLV-R5UC VCR is X-2625-356-2. The motor part number is 8-835-350--02. Check the winding on your motor. Many times when the bearing fails, it allows the magnet assembly to rise, which in turns starts to cut into the windings.
(Portions of the following from: blatter@amiga.icu.net.ch ((Martin A. Blatter)) Belts and idler tires are always the first thing to check for this sort of problem but older Symphonic/Funai VCRs (Those without the 'quickstart' type mechanism) also have a small rubber bumper/stop for the brake levers, etc. on top of the deck by the tape reels. It wears out and then the lever catches don't engage properly. The old mechanism was replaced by a compact direct drive type which is mounted directly on the PCB in 1993 (at least on the European PAL models). Part #8059-02-23 is available at electronics distributors such as Fox International in Ohio or MAT Electronics in PA. Symphonic/Funai Corp, 100 North St, Teterboro, NJ 07608 phone 201 288-2606. Alternatively, just wedge a bit of plastic inside the rubber bumper to fatten it a bit or just turn it around to expose the unworn side. This works just as well as a replacement part.
(From: Tony Buffone (uproc@Aol.com)). On the subject of the funai type rubber bumper problem I would like to give an additional symptom of that problem. After repairing hundreds of these units one goofy symptom I've found is the fact that customers may complain that the machine will eject a tape that is fully rewound and will play a tape if it is anywhere else on the tape. The FF/REW problem may or may not show up at this time. Also note that the best cure is the original part from symphonic. I have found that generic bumpers from MAT or MCM for example have cost me callbacks because there just not cut perfectly. (From: Matthew L. Kruckeberg (MKRUCKEBERG@pol.org)). I have run into a few of these Funai mechanisms where the replacement rubber bumper is too thick causing the mechanism to lock up in various positions. If you still have the original one try reinstalling it backward and see if your problem goes away. I would not recommend turning the bumper around permanently since the repair is short lived due to deterioration of the rubber but it will generally work at least for test purposes.
"Has anybody had any experiences with a Zenith VR2422HF VCR having auto-track problems with certain rental tapes? This is the second one I've had in the shop where it will switch back and forth between sp and SLP speeds. has anybody seen any mods or heard anything?" This is a common problem with certain Zenith VCRs. It is caused by the copy guard present on certain rental tapes. Zenith will modify these VCRs at no cost. The modification inverts the sync pulse by adding a transistor, a resistor and modifying the circuit board. If the model number starts with VRJ or VRL (possibly others as well), this is likely to apply. If you don't want to do the modification yourself but really want to sound like you know something, suggest that the problem is covered by Zenith Field Service Bulletin #94-16 :-). Two very similar modifications follow: (From: Guitarzan (guitarzan@aol.com)). Locate IC201 on left of top circuit board and IC 202 on right. Cut the trace between IC201 pin 56 and IC202 pin 17. I've found it easier to remove the wire jumper directly beside pin 56 as this leaves a place to mount the transistor. Install a general purpose NPN transistor (ECG123A, Zenith 921-2161 or 921-2134, or 2N2222) with base to IC201 pin 56, emitter to ground, collector to 10K 1/4 W resistor, other end of resistor to W2H5, or another +5 V source. The current drain is very minimal so pick the most convenient source of +5 V. All this does is invert the servo pulse and keeps the circuit from becoming 'confused'. If only it would do the same for me. Fire it up and all should be well. Try an EP tape, if its installed incorrectly, EP won't track at all. (From: Brian Hughes (bkhughes@usa.net)). Required parts: Small signal NPN transistor (ECG85, ECG2357, KRC103M), 10K 1/4 W resistor. Locate IC 201 on the main circuit board, cut the trace between W2C4 and IC201 Pin 56. Solder resistor between W2C4 and W2H5. Solder transistor as follows: Base - IC201 Pin 56, Collector - W2C4, Emitter - IC201 Pin 5. Insulate all exposed leads ( I like hot-melt glue, it secures things in place as well.) Finis. Why it works: Many pre-recorded tapes have timing marks inserted in the control-track signal. These extra pulses confuse the servo circuit in these machines. This modification inverts the signal before it reaches the servo so that it is not detected.
The flying video heads in a VCR or camcorder are the actual transducers which scan the tape during REC and PLAY. The head drum or upper cylinder, as it is often called, spins at 1800 RPM (for NTSC, actually 29.97 Hz) with one complete rotation representing a video frame (525 lines in the US consisting of 2 fields which are interlaced). The result of the spinning head is to provide an effective head-tape speed of over 24 feet/second needed to achieve the required video bandwidth. The actual video heads are the nearly microscopic transducers that contact the tape and magnetically record or playback the video information. The upper cylinder is the entire rotating assembly including the video heads. The heads are aligned and locked in place on the upper cylinder at the time of manufacture and this alignment should never be touched. (Note that the terms 'video heads' and 'upper cylinder' are often used interchangeably but strictly speaking this is not correct.) The heads themselves are made from ferrite which is an extremely hard ceramic magnetic material which is also very fragile. The head chips can be seen at the very bottom of the rotating upper cylinder. The actual construction is of a 'C' shape with a very small gap between the arms of the 'C' - about 1 um or so. This is filled with with a non-magnetic material to force the magnetic field out of the head into the tape and to prevent material from collecting in the gap. A few turns of fine wire form the coil of an electromagnet for recording and as a pickup coil for playback. If you look at a head chip from below (on a cylinder that has been removed) you can see the coil and the shape of the core, though you will not be able to tell if a head is bad or worn by this inspection unless there is obvious damage). A powerful microscope is needed to even see the gap. VCRs are described as having '2 heads' or '4 heads' or whatever. This actually refers to the number of head gaps and not actual head chips though usually this is the same number. However, two head chips may be placed very close together and thus appear to be a single head when in fact there are a pair of head gaps. Therefore, without a close examination, there may only appear to be 2 heads when in fact there are 4 - in 2 pairs. You are not being short changed. Two heads are required for any play, record, or search function. Usually, these are exactly 180 degrees apart - directly opposing one another on the upper cylinder. With 4 head (or 3 head or 5 head) VCRs, various combinations of heads are used for each mode to optimize record or playback video quality by selecting a pair of heads with optimal widths and other characteristics. These may end up not being exactly 180 degrees opposed requiring video delay line to line up the two video fields in a video frame properly. This complicates head testing as it is not always obvious even which set of heads is used in any given mode. An additional pair of opposing heads is required for HiFi VHS audio and another one is present if the VCR has flying erase head. Usually, there is only a single flying erase head - it is double width and clears a pair of tracks (fields) on each pass. So, there may be up to 7 (or even more) heads competing for space on the upper cylinder! Also, see the section: "Video head construction".
The actual video head chips themselves are mounted just about flush with the lower edge of the spinning assembly called the head drum or upper cylinder. They are made of ferrite - an extremely hard but fragile material. In terms of physical strength, its properties are similar to glass. The head actually consists of the core, pole pieces, and gap filler molded as a single unit and fired at high temperature along with the coil wound on the core after firing. This 'chip' is then glued to a metal support which is screwed to the bottom of the drum. A screw presses against this support from above and is used at the factory for final head height adjustment on the drum. CAUTION: Do not touch these mounting screws or the height adjustment screw accessible from above the drum. It is virtually impossible for these to become loose or misadjusted on their own and alignment in the field is not possible except by trial and error. These structures may be viewed under a strong (e.g., 10X) magnifier though the actual record/play gap between the pole pieces will not be visible except under a powerful microscope. It is filled with a hard non-magnetic material in any case. The thickness of the ferrite chip is about .1 to .15 mm but the width of the active part of the pole tips narrows down to around .03 mm. This is one of the dimensions that is optimized for various special effects in VCRs with more than 2 video heads. The gap azimuth angle of + or - 6 degrees (for VHS) is implemented by actually twisting the pole pieces during the molding process. This is actually visible if you look carefully with the magnifier even though you cannot actually see the gap. (The azimuth angle has obviously been exaggerated in the diagrams below due to the limitations of ASCII art.) The coil used to generate the magnetic field during recording and to sense the magnetic field for playback consists of a dozen or so turns of fine insulated wire with a typical resistance of 1 to 1.5 ohms. HiFi audio head construction is generally similar except that the gap azimuth angles are +/- 15 degrees instead of +/- 6 degrees. Damage to the core, pole pieces, or coil, and oxide on the surface or clogging inside of the core can be seen with the magnifier in many cases.
The diagram below shows a typical single video head as would be found on
a 2 head VCR. Two of these (with opposite gap azimuth angles) would be
mounted exactly 180 degrees apart on the upper cylinder. This is a view
as would be seen from the bottom of the upper cylinder:
____________________________
| |
| _______ |
Coil+ o---------------+ | |---o Coil-
+------------+ +-----------+
. +------------+ +-----------+ .
. +------------------/ | .
. | \ / | . Side of upper cylinder v
-----------\____________||____________/---------------------------------
-->||<-- Record/Play gap, width about 1 um The same head viewed from the edge: ______________ _____________ Bottom of upper cylinder v |_____________//_____________| | | |<---------- 1/8">|
The diagram below shows a typical double video head as would be found on a VCR
with more than 2 video heads if video heads are grouped together. The quite
visible space in between the two head chips should not be confused with the
actual microscopic record/play gaps in the pole pieces even though the total
width of the two head chips (1/8") is about the same. For a 4 head VCR, there
would be two such assemblies (with opposite gap azimuth angles for each head)
mounted 180 degrees apart on the upper cylinder.
This is a view as would be seen from the bottom of the upper cylinder:
Coil1+ o o Coil2+
___________________ | | ___________________
| || || |
| ______ || || ______ |
Coil1- o---| | +----+ +----+ | |---o Coil2-
+-----------+ +----+ +----+ +-----------+
. +-----------+ +----+ +----+ +-----------+ .
. | \---------+ +---------/ | . Side of upper
. | \ / | | \ / | . cylinder v
--------\____________||___/-----\___||____________/---------------------
-->||<-->||<-- R/P gaps, widths about 1 um The same head viewed from the edge: Bottom of upper ______________ ____ ____ ______________ cylinder v |_____________//____| |____\\_____________| | | |<------------------ 1/8">|
The following site has photos of a variety of typical 2, 4, and 6 head
assemblies as well as 8mm and VHS-C camcorder heads.
* http://www.shadow.net/~gury/vh1.html
They also sell video heads and will quote prices by return email. I have
not purchased anything from him so I cannot say anything about his prices
or service.
The rotating upper cylinder and stationary cylinder form a transformer - the space between them is very small and coupled the signals between the primary and secondary ferrite cores. Each of the heads for R/P video, HiFi audio, and flying erase, are electrically independent. The cores are arranged coaxially which should get to be pretty tight for a 6 or more head VCR!
No picture (total snow or a blue/black screen depending on model) or a snowy picture in play modes and/or failure to produce a good recording may indicate dirty or bad video heads. First, make sure that the VCR's tuner and RF modulator are working by viewing a broadcast or cable channel. Next, refer to the section: "Video head cleaning technique" and follow the instructions carefully. If there is no change even after a couple of cleanings, then your video heads may have problems. Of course, if your inspection reveals any physical damage, you will need a new set of heads (new upper cylinder). Indications of a bad video head include: * Any visible damage to the ferrite chips. Heads nearly always appear in opposing pairs on the upper cylinder (head drum). Any visible discrepancy between the chips in a pair is probably damage. Sometimes 1/2 of the core breaks off leaving the windings dangling. Common causes for this damage are improper cleaning techniques or the use of damaged or spliced tapes. Use a magnifying glass and bright light to examine the heads but do not touch! By the way - improper splicing of broken video tapes is a good way to break video heads. Any kind of splicing should be avoided if at all possible. (See the section: "Recovering damaged or broken tapes".) * Excessive video snow which cannot be eliminated by the tracking controls. The appearance may also be of trailing lines or bullet shaped streaks particularly following highlights. Note: in rare instances, similar symptoms are the result of a static brush not making proper contact with the shaft of the spinning drum. See the section: "Firing (static) lines in picture during playback". An image where more or less good video alternates with snow at a 30 Hz rate means that one of the 2 heads in a pair is probably either dirty or bad. If your TV has a wide range vertical hold control (yeh, right, give me a time machine), then you may be able to display both fields on the screen at the same time. * Excessive video snow or no picture (total snow or blue/black screen depending on model) for some playback speeds (SP, LP, EP, X2, still, slow, etc.) since different sets of heads (in 4 head or more) machines are often used for different speeds. If this is due to wear, then it would probably gradually deteriorate and not happen suddenly. * Inability of certain internal adjustments such as backtension to eliminate erratic tracking problems may indicate a worn video head. Horizontal bands of video noise may come and go at various places in the picture depending on what speed is being used or the playback location on the tape (beginning, middle, end). These may come and go in a periodic cycle. * Need to frequently clean the video heads even if you are only using new good quality (name brand) tapes. Video heads are normally self cleaning but very worn heads can tend to collect tape oxide resulting in a noisy, snowy, or totally missing picture. * You have just been playing a rental, damaged, or spliced tape and you notice any of the above symptoms. The video heads may have picked up some oxide and are no longer making proper contact with the tape. Letting the VCR play a newer tape for a few minutes may clear this if it is minor. Otherwise, video head cleaning (using the proper technique!) will be needed. However, seriously damaged or improperly spliced tapes can result in serious damage requiring video head (upper cylinder) replacement. If your VCR has HiFi audio, similar symptoms may apply to the HiFi audio heads on the rotating drum. Noisy or loss of HiFi audio or erratic switching between linear and HiFi audio may be due to bad HiFi audio heads (but could also be a tracking problem since HiFi audio tracking can be even more critical than video tracking). However, many other problems can result in similar symptoms - video head diagnosis is one of the most difficult to make (except for physical damage). Some pros claim to be able to determine if a video head is worn by feeling it with a finger. I can guarantee that you will not be able to do this, so the set of guidelines given above is the best to go on.
From: Frank Fendley (frank.fendley@datacom.iglou.com)). It depends on what's wrong with the picture. If you are getting "highlight streaking in high luminance areas" (meaning that white objects in the picture seem to have "tails" trailing off to the right of the object), then a new head would help immensely. If there are random lines in the picture (especially on tapes you have recently recorded on that machine), then a new head will most likely help. If the picture just isn't as sharp as the VCR next door, then a new head probably won't help much. Technology has improved picture quality considerably since your VCR was manufactured. One recommendation - if you want the best picture quality from *any* VCR, forget about recording programs in SLP or LP. The SLP (or EP) speed should be banned and made illegal - the picture and audio quality are terrible. LP should only be used on programs which exceed 2 hours. You should use SP speed on everything you record if at all possible.
When should you clean a video head? Only when symptoms point to a problem with the head. See the section: "Are your video heads really bad?". Periodic cleaning is not necessary and may cause excessive wear if done with a head cleaning tape, especially the dry kind which may be excessively abrasive. Frequent cleaning by hand, while not damaging, still represents a slight risk since you never can tell when you might do something you will regret! VCRs should be cleaned periodically, but video heads usually do not need periodic cleaning as the spinning heads performs a self cleaning function. If it ain't broke, don't fix it.
I do not see any advantage in buying a VCR which claims to have automatic video head cleaning. Healthy vVideo heads are basically self cleaning in any case. The automatic head cleaner is a foam roller that contacts the rotating heads for a couple of seconds when the tape is loaded. In my opinion, this is worse than useless as any crud collected by this foam may just be redeposited on the heads during the next cleaning cycle. So, if your VCR has this 'feature' and you experience symptoms of dirty video heads after each tape, remove the 'feature' and performance will improve :-). As noted below, there is a slight risk that at some point they may actually destroy the video heads - no doubt timed to be 1 day after your warranty runs out :-(. In addition, they do nothing to clean those portions of the VCR that really may need periodic maintenance like the rubber parts, A/C head, and tape guides. The only benefit of an automatic head cleaner is to the manufacturer of the VCR as it increases their profit margins! (Portions from: Joseph E. Fealkovich (jef812@ix.netcom.com)). I would pull those 'automatic head cleaners' out and let the customer know about it. I hate those things, they do more trouble than good. The least they can do is redistribute the garbage back onto the heads, the worst, actually catch on a head and tear it right out of the drum, (I've seen this happen on a Goldstar VCR). When new, they do a fairly good job 'dusting' off the video heads, but they wear out quickly, (they work every tape loading and unloading cycle), and can seriously ruin the heads. Furthermore, they clean only the video heads when they work; they do absolutely nothing for the grooves cut into the drum, I'll say that's the most important part, as the grooves form an 'air bearing', where the tape floats on the drum, without that that effect, the heads can wear out prematurely due to the tape sticking to the drum. My opinion on 'self cleaning' VCR's is, they've done just about everything dumb and automatic on these VCR's.
The following is a true story. Don't let it happen to your VCR! Read the section: "Video head cleaning technique" before breaking out the pliers and sandpaper (well almost). (The following is from someone who not surprisingly would rather remain anonymous). "Thanks a lot for the FAQ on VCR repair (unfortunately too late --- sam). I now realize that I have made a boo-boo of quite unprecedented magnitude!! You're not going to believe this... (I'm almost too ashamed to admit to this!). My friend asked me to clean the heads on his VCR. I got out my isopropyl alcohol spray (good) and my cotton buds (not good!). I proceeded to scrub the upper drum furiously, getting lots of lovely black deposits on the cotton buds. I, ahem... also scrubbed vigorously around the four little 'recesses' positioned around the bottom of the drum. When I spotted a little bit of metal sticking out of one of the recesses, I got out my tweezers..... (You can stop reading here if it's too painful!) ...and poked around, thinking 'this will cut the tape to ribbons if I don't get it out'. After succeeding in removing the offending piece, I noticed a very fine copper wire emerging from the hole too.... OUT IT CAME (with the tweezers of course). I checked the other three holes and succeeded in removing some more shrapnel from one other. Guess what? It wouldn't play properly after this.... but the sound was OK. To be fair, I was fairly sure I'd screwed up big time when I saw the copper wire... but of course it was far too late by then. I admitted to my friend that I thought I'd broken his video head and that I would replace it for him. Thinking that heads cost around the $30 mark, according to most of my catalogs, I was horrified when I got a price for his particular model.... $162.00 + 17.5% tax and postage..... However, this was much less than what the original manufacturer wanted: #350!! Well, I finally found a replacement for $85. Still, an expensive lesson."
Caution: Read the following in its entirely to avoid an expensive lesson. As noted, improper cleaning can destroy your video heads. The head chips are very fragile and just rubbing them in the wrong direction (NEVER use an up-and-down motion) can break the chips off requiring replacement of the entire upper cylinder assembly - one of the most expensive parts in your VCR! Manual cleaning using the proper head cleaning sticks is best but requires that you gain access to the interior of your VCR - i.e., take off the cover. If you do not want to do this, you can try a commercial wet cleaning tape. These is some slight risk, however. The material used in some of these may have an excessively coarse fiber structure which can catch a video head and break it off. I have not seen this happen nor could I recommend a specific brand as there is no way of knowing what their current product uses. I do not recommend the dry type at all as these are almost always much more abrasive and may cause premature wear of your video heads especially if used regularly. When using the wet type cleaning tapes, follow the directions and - very important - wait sufficient time for everything to dry out or else you will have a tangled mess inside your VCR. Regular video head cleaning should not be needed! Therefore, the regular use of a cleaning tape is not recommended. As noted, some cleaning tapes will cause excessive wear to the video heads and no cleaning type can adequately deal with other parts of the tape path anyhow. If you find yourself needing to clean your video heads frequently, the video heads may be worn, the backtension may be set too high, or you may be playing old or dirty (literally) rental tapes. To clean by hand, you will need what are called 'head cleaning sticks'. These are covered by chamois and are safest. DO NOT USE Q-TIPS (COTTON SWABS). These can catch on the ferrite cores and damage them or leave fibers stuck in the heads. Q-tips can be used for cleaning the other parts like the rollers and audio/control head as described above but not video heads. To use the cleaning stick, moisten it with head cleaner or alcohol. Pure isopropyl is best, however, the 91% medicinal stuff is ok as long as you dry everything pretty quickly. Don't flood it as it will take a long time to dry and you run the risk of any water in the alcohol sitting on surfaces and resulting in rust (very unlikely, but don't take the chance). Gently hold the flat portion of the chamois against the upper cylinder where it is joined to the lower (non-rotating) cylinder. Rotate the upper cylinder be hand so that the heads brush up against the moist chamois. DO NOT MOVE THE HEAD CLEANING STICK UP-AND-DOWN - you will break the fragile ferrite of the heads - $$$$. Side-to-side is ok as long as you are gentle. (The following tip from: Steve (sreed@amsupply.com)): A good quality automobile chamois (the real thing, not the fake stuff), cut up into 1 to 2" squares, is far cheaper and easier to manipulate than the sticks. After cleaning the heads, the chamois square can be re-moistened with cleaning fluid and used to clean the A/C head, rollers, guides, etc. There is another advantage to this approach. The chamois sticks can on some occasions "catch" on a video head, because the chamois area is small and the edges are rigid. Using a larger cut-up square of chamois eliminates this problem because the edges of the chamois are away from the rotating head and you're simply holding it against the drum with your index finger." I know people who use a piece of moistened typing paper or a business card, or even their Mark-1 thumb for video head cleaning but I would not recommend these for a general service procedure! (I suppose the only real requirement to prevent damage is that the material have a fine enough structure and not have fibers that can get stuck in the heads. So, the short list of acceptable materials is quite long - some more effective than others. My concern for a general recommendation is that people's interpretation of these requirements can vary quite a lot. If a novice comes to me and asks what to use, I will say 'cleaning sticks'. Once they understand the characteristics of the heads and their mounting, they are free to use whatever works.) Depending on how dirty your heads are, a couple of passes may be enough. Let everything dry out for at least 1/2 hour. This may need to be repeated for stubborn clogs. However, one pass will often do it. In addition, inspect and clean the drum itself staying safely away from the video head chips. The five fine grooves in the drum help control the air bearing that the tape rides on and helps to stabilize tape motion. These should be clear of dirt and tape oxide (DO NOT use anything sharp - the moistened head cleaning sticks will work).
(From: Rob-L (rob-l@superlink.net)). As an alternative, I'd use a *dry* bit of paper. Moderate finger pressure against the whole side of the drum, overlapping to the motor assembly. Then twirl the drum in each direction a few times. Look at the paper and you'll see exactly where the dirt is coming off. Once you can do this and get no marks, you're heads are relatively clean. A tiny, soft, short brush and a puff of air will dislodge any paper fibers. The paper and its fillers are generally not going to harm the drum/ferrite-chips with this brief contact. And you can pop a tape right in without waiting for solvents to evaporate. Besides, solvents may soften any encapsulants on the chips, and cause residue to get on the polished surface. Once in a while, I run into a set of heads that seem to be bad, even after cleaning with different methods. This is characterized by poor signal strength in all or part of the picture, sometimes one field only, and sometimes tracking range is extremely narrow as a result. On S-VHS units, S-VHS recordings get noisy and may get blanked, while the same unit will work in VHS with minor tracking problems. Upon 30x pocket microscope inspection of the heads, I find a speck of what appears to be a cloudy polymer, firmly bonded to the edge of one or more of the chips. How did it get there? My guess: too much solvent - may have dissolved encapsulant and/or dust that was at the edge of the chip. Solution: *carefully* drag a jeweler's flat-blade screwdriver along the chip (under magnification). Sounds a bit risky, but this has never damaged a head in my hands. Follow this with a final paper-buffing, and usually the VCR is tracking fine, with a much improved picture. Saves mucho bucks. 'Course, sometimes the heads are just plain worn out. My advice: Invest in a pocket microscope before you start pricing heads.
Assuming cleaning does not help and you have the time and inclination, some additional test can be performed to confirm or rule out a bad set of video heads (upper cylinder). To check the signal from the video heads you need a circuit diagram so that you can locate the relevant test points and expected voltage levels in the head preamp. This will be housed in a metal enclosure, usually right next to the head assembly (at the rear). This should be done with an alignment tape, but any known good recording should provide a reasonable approximation. Other basic checks such as visual check with a magnifying glass, continuity tests on the heads as well as power supply voltages in the preamp can also help. If your VCR has 4 video heads (not including HiFi audio heads) and only certain modes or speeds do not work, then the following procedure may permit you to isolate the problem to a head or its preamp. Basically, the idea is to interchange the wiring of the two pairs of heads. While the heads will no longer be optimized properly for each mode, there is a good chance that they will work well enough to determine gross changes. For example, if SP play originally had alternating fields of good and bad video and works moderately well after this rewiring (but maybe with tracking noise), then you know that the bad head is no longer being used for SP play. Since the same head preamps are being used, a bad head must be at fault. Video drums where the heads are wired with flying leads are somewhat easier to cross-wire than those with a PC board. This is not fun and may not work in all cases, but if you are hesitant to risk the cost of a new head, it may be worth a try.
You mean your thumb isn't calibrated to the micrometer (um)? "I'm trying my hand at VCR repair. Sony specifies a hand-held device that connects to a non-rotating video head and that measures how worn the head is (beta machine). I'm trying to imagine how it works. Is it the head gap itself that gets bigger as the head wears? (From: Raymond Carlsen (rrcc@u.washington.edu)). There is (was?) a device to check for head wear by measuring the inductance of the head itself. The head must be disconnected from the rotary transformer, of course. Older machines had wires on top of the head that could be easily disconnected (like the Beta decks) without removing it. Heads on some newer machines must be removed from the VCR because the leads are underneath. Apparently, the inductance of the head changes slightly as the ferrite material wears away. The head gap itself doesn't change as the head wears. If the gap were to open, the head wouldn't work at all, and I assume that the inductance would be significantly different than a used good head. In most cases, the head chip(s) wears to the point that the tip penetration is not sufficient to keep it in intimate contact with the tape. The heads tend to clog more easily as they approach end-of-life. The inductance type of head tester does have a few drawbacks. It's rather expensive, and to accurately tell how much usable life a head has left using only the tester, you must have a "sample" of exactly the head under test for comparison... each one is different. The measurement is relative, not a "good-bad" reading. All that said, I have been using my finger (and a microscope) for the last 10 years to tell good from bad, and to estimate usable life . I learned to gauge the tip penetration by feeling the rotating head chips as the tape is moving through the machine. A well-calibrated finger placed lightly on the tape on the exit side of the drum is very revealing. Streaking or comet-tailing on recordings of small bright objects usually means the heads are close to being worn out (gap starting to open up). A microscope is good to check for the more obvious broken or chipped head, and to see if a stubborn clog is actually gone. Different VCR brands will show different results to my finger test: old Hitachi decks will show bad heads before they actually "feel" worn out... one usually goes first, producing alternating fields of snow and picture. I've seen a few older Panasonics that still worked even when the heads were worn down where they couldn't be felt any more. How do you tell the difference between worn out heads and a head clog? Clean the heads and try it again... then feel it. Tentel Corp. makes a test fixture that actually measures tip penetration, but with a bit of experience as a guide, the best test instrument is still the mass of grey mud between the ears. (From: Frank Fendley (frank.fendley@datacom.iglou.com)). There are two methods (that I know of) which measure wear on video heads. One is a protrusion gauge, which measures how far out the heads extend past the edge of the drum. Once the heads fall below a minimum extrusion, they are considered worn. It's similar to measuring the tread left on a automobile tire. The other is a "Video Head Tester", sold for either Beta or VHS models. Essentially it is an inductance bridge. You connect each head to the test leads, calibrate the unit, and then measure the inductance of the head. The theory here is that as the head wears, its inductance goes down due to loss of the core material. Past a certain minimum, the head is declared worn out. Bear in mind that a head could fail both of the above tests and still give a good quality picture (although it is true that its days are probably numbered). It is also quite possible that a head could pass either or both of the above tests and be defective. Are the the testers worth it? In my opinion - probably not, unless you are a real purist and like to have a lot of test equipment.
Remember how I told you never to even think about adjusting the video head chips themselves? Well, it seems some people never listen :-). (From Jerry Greenberg (jerryg@total.net)). I researched out tip penetration specs on video heads for VHS and Beta (home) machines. I got a number of people interested in this one to the point that a few machines came off the shelf, and the research began. We had the tools at our disposal to get this done. The following measurements are in mm (millimeters). Brand new heads off the shelf in both Beta and VHS were about 0.12 to 0.16 mm penetration. At about 0.05 mm the video signal starts to degrade. But the head will still record well. At about 0.02 mm the video is very noisy. If you loosen the head and push it out a bit, you improve it slightly. But, the gap is now wider. Therefore, the signal is a bit stronger (due to the additional penetration) but has more noise. Overall, a slight improvement. Also the horiz angle of the head effects the switch point a bit. If out, a slight horizontal jitter (flag waving) is noticed, and the PG is slightly out. You can correct with the PG adjust to a point, but the head effective angle from the opposite one must be better than 2 deg. As the head wears, we found that the head surface leaves the tape too soon, and starts reading the tape too late. If the heads are down to about .05 mm the effective error (both heads summed) is about 2 to 3 degrees. The puts it slightly out of spec for the switch-over point and causes some instability. This problem is also summed because the carrier output is at about 60% of the normal amount. As the head wears from this point, the carrier drops more rapidly. It is not linear. It follows the inverse square law factor.
Highlight tearing - trailing lines adjacent to bright areas of the picture - often indicates a worn video head. Sometimes, this only shows up severely for tapes recorded AND played back on the same machine. Why? (From: Jaclyn (lambert@sos.net)). The reason why it **appears** to be a record only problem is fairly straightforward if you understand what's up. When you make a recording with bad or marginal heads the resultant recording is poor. Perhaps a vcr with good heads will be capable of producing an "acceptable" picture, perhaps not. Depends on the alignment and how good those heads are. When you try to play the "poor" recording back on the vcr in question the resulting performance is unacceptable because the heads on that vcr are marginal at best and are simply not going to have the gain required to pull the crappy recording off. Get it? It's a double whammy two fold effect. Video heads don't just go "bad". They wear down after time and early symptoms sometimes also include poor vertical stability (as is so common in Hitachi VCRs) and snow "lines" which hover about 2 inches from the top of the screen. Occasional loss of horizontal sync is also typical.
Once you have concluded that a replacement head is required, you need to decide whether you will undertake this yourself or take the VCR to a shop. Video head replacement is relatively straightforward and low risk as long as you are comfortable working on mechanical devices and take your time. A little unsoldering and soldering is usually required. Electronics suppliers such as MCM Electronics, Premium Parts, and Dalbani stock a wide range of video heads for VCRs that are more than a couple of years old. (They may not have heads for the latest models.) In some cases, they will offer two kinds of heads for the same model - a generic version and a 'name brand'. Unless you are extremely critical, there is probably no need to spend the extra on the 'name brand' head. There is also no need to pay the premium charged by the original manufacturer of your VCR - it is often priced 2:1 or more over what a generic head will cost with no substantial difference in performance, if any. You may even end up with exactly the same head manufactured on the same assembly line! Note that currently, the price of many upper cylinders (video heads) for 2 head VCRs is well under $25 so ordering a replacement may be a better investment of time and effort than a long diagnostic procedure especially if the old head has high mileage and video quality has been steadily decreasing.
On some newer VCRs, it seems that in the manufacturer's infinite wisdom (or cost crunching), the normal video head drum or upper cylinder cannot be replaced by itself. Only the entire expensive cylinder unit is available. Unless you can find a junk VCR (try Allbrand, see the section: "Used VCR parts"), repair may be too expensive. Just buy a different brand next time, which, of course, may not matter :-(.
1. Do not touch the actual video head chips themselves. Handle the head as little possible. You can touch the upper part of the head cylinder if necessary. One thumb through the center hole with fingers resting on the upper edges works pretty well. 2. Before you unmount the old one, mark or make a note as to its position - sometimes it is possible to mount the new head 180 degrees off from way it is supposed to be oriented causing tracking problems at the least as the opposing heads are not identical. (The azimith angles are +/- 6 degrees for VHS, +/- 30 degrees for VHS HiFi audio). Also make a note of the wiring if there is any possibility of confusion (i.e., there are individual wires, not connections from below to a printed circuit board). 3. Unsolder the connections between the head and the upper cylinder. There will be 2n solder connections for an n head VCR. (Sometimes there is some kind of connector rather than solder connections, but this is rare.) Examining the new head should reveal exactly where to unsolder. For pins through the printed wiring board type, you should use some kind of desoldering tool - solder pump, SolderWick, or a vacuum rework station. In rare cases where there are individual wires, a generic replacement head may not be color coded the same or have the wires originating from different places than the original. In this case, you will have to try to determine which physical head chip the wires originally connect to. You must get each of the connections from the lower cylinder to the head in the same physical head as before (though the polarity or phase of the pair of connections to each head should not matter). 4. Unscrew the 2 or 4 philips head screws holding the old head in place. It should be obvious from the new head which screws need to be removed. You may need to remove the static brush if your VCR has one or some other usually obvious stuff to get at it. DO NOT touch any other screws on the head drum as these are critical adjustments one should not mess with. 5. Lift the old head straight up and off. You should not need to use any drastic measures though a little jiggling may help. I have never actually needed a head puller. 6. Replace in reverse order, solder the connections, replace any other hardware that was removed. Refer to your notes on the position of the old head and/or the color codes (wire colors, dabs of paint, etc.) as to orientation on the drum. 7. Carefully clean any fingerprints from parts of the head drum you touched. Again, do not touch the video head chips themselves. You may use 91% medicinal alcohol, though pure isopropyl is preferred. Avoid rubbing alcohol especially if it contains any additives. Let the machine dry completely. 8. Unless you tweaked any mechanical adjustments, the VCR will very likely work fine assuming the video head was the problem. Try recording and playing back at all speeds as well as playing pre-recorded tapes as well. Carefully examine the video for excessive snow, jittering, or tracking problems. For HiFi VCRs, also confirm that the HiFi audio is solid and stable - that the HiFi light is not flickering in addition to audible dropouts or muting. If the tracking is now way off or you experience serious video noise, lack of or erratic color, or bad or missing HiFi sound, refer to your diagram and double check that you didn't replace the head rotated 180 degrees from the proper position by accident. Make sure the drum is seated properly - not on a bit of dirt on one side. DO NOT be tempted to adjust tape path alignment - if the heads were the problem, it should be fine. Also see the section: "HiFi/video tracking problems after upper cylinder replacement". It is a good idea, however, to perform what is known as the 'Tape Interchangeability Adjustment' (this terminology is used in Panasonic VCR service manuals, meaning is self evident) in any case. This procedure consists of adjustments to the roller guides, other guide posts, and the A/C head. See the chapter "Tape Path Alignment and Backtension Adjustment" or follow the set of steps in your service manual. On rare occasions, some electronic adjustments will also be required to obtain optimum video quality but this is the exception rather than the rule. Tapes recorded at EP speed will almost always be more finicky and may require these adjustments more so than those recorded at SP speed.
(From: Raymond Carlsen (rrcc@u.washington.edu)). If it's a Samsung based machine, you might need a head puller. I got one at a service seminar many years ago and need it once in a great while to pull a stubborn one, usually a Samsung. Avoid the temptation to pry up with screwdrivers. I've seen the results of such abuse... not pretty. Look for threaded holes in the head drum. That's a clue it needs a puller, which attaches to the head drum and presses downward on the center spindle with a few twists of the handle. The new head (also a tight fit) is seated by alternately tightening the two mounting screws. You could make a puller with a bar of metal and some long screws. Drill two holes in the bar to fit the spacing of the threaded holes in the head wheel and one in the center between the other two. Tap the center hole (8-32 is big enough). Use screws (small metric) long enough to thread into the drum to attach the bar. Run a screw down the center hole until it contacts the center shaft of the drum. Keep rotating until the drum pulls off.
There are a number of possibilities and one of the more common particularly with generic replacements is, guess what? A defective replacement! When replacing the upper cylinder, the orientation and wiring must be exactly the same as the original. For many VCRs, this is automatic since the mounting is keyed and the wiring is via direct printed circuit board connections. However, there are also many where it is possible to screw up either the orientation or wiring or both: * For lack of color, erratic color, excessive video noise, and tracking problems double check its orientation. Accidentally replacing the head drum 180 degrees from its correct orientation will result in a variety of video quality problems. * Where individual wires are used rather than soldered connection to a printed circuit board from below, make sure you have attached the lower cylinder terminals to the proper heads. Some generic heads apparently do not have the identical layout. It may be necessary to visually trace the wiring on the old and new upper cylinders to determine which actual video/HiFi audio head chips are attached to which wires. Also don't assume that the wiring color codes are same! However, you are lucky in one respect: The polarity or phase of the pair of connections to each head should not matter!
Unless you had such symptoms originally where best settings of the tracking control for the HiFi audio and video are at grossly different positions, the problem is with the video head drum itself or its installation. (From: John R. Hepburn (jhepburn@recorder.ca)). If you have an oscilloscope and service manual, check the envelopes for maximum output. Audio and video should max at roughly the same tracking position. If they do, forget about heads or any mechanical problems, it is electronic (but probably existed before the replacement - possibly masked by an originally defective set of heads!). If they do not, then it is probably a drum problem. DO NOT adjust your roller guide height or any other posts! They were in the right position before (unless you have already moved them) so they are in the right position now. Minor post adjustments are OK after heads are replaced, but that is just to peak it out. No serious problem has ever been solved on a VCR by adjusting posts that are in their original position. Remove the heads and check for proper seating. You would hate to make a big deal out of this, only to find one side of the drum was seated on a small piece of residue.
Since video heads are not all manufactured exactly the same, there is a slight chance that you will experience problems of playing tapes recorded on other VCRs in yours. However, before adjusting the roller guides or other settings, make sure that the *other* VCR is aligned properly. (From: John F. Reeves (jreeves@uwf.edu)). Take an alignment video-cassette tape and verify that the P2 and P3 posts are adjusted properly. you should use a scope and monitor the RF envelope while adjusting the above mentioned posts. Once this procedure is done, make a recording and play it back in another VCR. If it still does not track properly, it may necessary to perform the tape interchange ability adjustment. This adjustment in more critical and more in depth, should be performed be a qualified technician.
Suppose I screwed up and installed a video head 180 degrees rotated from what is correct. What will happen? First confirm that it is even possible to do this - some are keyed in such a way that a hammer would be needed. The effects will depend very strongly on the particular VCR but the following are among the possible symptoms: * Tracking that is way off for tapes recorded on another (properly adjusted) VCR. It may be so bad as to be beyond the correctable range with the user tracking control. The azimith angles of the head pairs are opposite of what is expected and this directly affects tracking. * Noisy picture or no/erratic color in some or all play and search modes. On 4 or higher head VCRs, even opposing pairs of heads have different characteristics so these will not be matched to the electronics with the head on incorrectly. * Flying erase will not work where only a single flying erase head is used. To test for this (assuming your VCR has a flying erase head), record over an old recording. If flying erase is not working, you will get a rainbow pattern (assuming you get any color at all) which will wipe down the screen over a 10 second or so period (just like a VCR that lacks flying erase). The 7th head in a 7 head VCR is likely a flying erase head.
The quick (and long) answer is: NO. The heads themselves are in no way standardized. You can substitute a video head drum (upper cylinder) if it is identical - VCRs sold under different labels are often manufactured by the same few companies. Check a cross reference if you have a dead VCR with a good set of heads but not the same model as the one you are trying to repair. As far as the heads themselves, don't even think about attempting to interchange the actual head chips - even if your replacement were physically and electrically compatible, you would never be able to get the alignment within tolerance since you do not have the factory jigs. Not to mention that the head chips themselves are really really tiny and really really fragile and their specifications all vary - head width, azimith angle, etc. Forget it.
It is rarely necessary to do this but if you should - from curiosity or anything else - beware that the reference for the #1 head may be a magnet attached to the motor shaft. This may not be keyed and unless you carefully mark everything beforehand, will have no way other than trial and error to get if back at the proper angle.
There are separate descriptions of the procedures for adjusting the various components of the tape path - in particular, A/C head azimith, tilt, and height; and roller guide height. Before you attempt these, you need to determine whether either of these are likely to be your problems. For really major tracking problems with all tapes, check for broken or missing parts or for problems which prevent proper positioning of the roller guide assemblies during tape loading. Types of symptoms include: broken up picture, snow across part of picture, multiple breaks (sort of like the VCR is in a search mode such as CUE or REV but is not) in picture, totally unstable picture, or multiple of the above. Of course, someone before you may have messed with various mechanical (or heaven forbid, electrical) adjustments without having a clue of what they were doing.
The following are some symptoms you may experience indicating the need for A/C head adjustments: * Weak, muddy, or wavering sound. (Azimith, height, or tilt adjustment). * Tracking incompatibility between this VCR and tapes recorded on other VCRs - you always need to adjust tracking or keep the tracking control way off center when playing tapes from other VCRs. However, if it is only one other VCR, that VCR may be misadjusted. (Mechanical tracking adjustment). * Erratic loss of synchronization or frame lock, or speed changes. (Height or tilt adjustment). Before you try to adjust the A/C head, make sure that there is not some obvious mechanical problem that has shifted its position. There may be a bit of something stuck in the mechanism. If this appeared after you did some work on the VCR, you may have accidentally caught a cable or something else preventing the A/C head assembly from returning to its proper position. This is particularly likely if the problem happened suddenly. Once you change its settings, any tapes recorded on your VCR prior to these adjustments may not play back properly. For example, if you touch the A/C azimuth screw to correct a muddy weak sound problem when playing tapes from other VCRs, any tapes previously recorded on your VCR will now sound muddy and weak. You need to decide which is more important - your recorded tape library or compatibility with other VCRs.
The following are some of the symptoms you may experience indicating the need for roller guide height adjustments: * Video noise at top (supply/left side roller guide) or bottom (takeup/right side roller guide) of picture that cannot be removed with the user tracking control. * Video noise in various areas of picture that comes and goes in a few second cycle. For example, a few lines of video noise may travel up or down the screen or start at the edges and meet in the middle. (Misadjustment of either roller can cause these symptoms.) * A jumpy picture - as though the vertical hold control (which most TVs no longer have) is misadjusted. (The supply/left side roller guide is probably misadjusted.) Before you try to adjust the roller guide height, make sure that there is not some obvious mechanical problem which is preventing the roller guides from seating properly. This is particularly likely if the problems happened suddenly. See the section below on: "Likely causes for sudden change in tracking behavior". Gently check each roller guide to see if one is loose in its threaded mount. If one turns with finger force, that one is likely the problem AND YOU SHOULD NOT TOUCH THE OTHER ONE! Where both are loose or have been adjusted, it may take quite a bit of trial and error to get them both set correctly again. Try not to make this an issue!
While there are many variations on the exact locations of each of the A/C
head alignment adjustments, the following description is for one of the most
common layouts. See the appropriate sections elsewhere in this chapter for
the adjustment procedures for the A/C head.
* A/C mechanical tracking. This is a conical nut on a small shaft fastened to
the transport base. It is wide on top and tapers down below. A slot across
the top allows the nut to be turned and thus raised or lowered. Its angled
side presses against a projection on the A/C assembly base plate. Thus
raising or lowering the nut moves the A/C head assembly from side-to-side.
- When raised (counterclockwise), the A/C head assembly moves away from the
video heads increasing the delay between the video and sound.
- When lowered (clockwise), the A/C head assembly moves toward the video
heads decreasing the delay between the video and sound.
You may need a special screwdriver with a cutout in the middle of its blade
(or modify one of your own) to easily adjust this nut.
* A/C head height - A hexagonal nut on a large shaft behind the A/C head. This
moves the entire A/C head assembly up and down. A spring underneath provides
both the upwards pressure to keep the A/C head assembly against this nut and
torque to keep it against the conical A/C mechanical tracking nut.
* A/C head tilt - A Philips screw is directly behind the A/C head on the plate
that the head sits on. This adjusts the A/C head forward and backward (with
respect to the tape).
* A/C head azimuth - Another Philips screw is to the right or left of the head
on the same plate just mentioned. It probably has (had) some red (or other
color) paint on it to lock its position. This adjusts the A/C head azimuth
angle (side-to-side) with respect to the tape.
* A/C head plate pressure. A third Phillips screw (on the opposite side of
the A/C head from the azimuth screw) with a spring under it. This should
just be left alone as its only function is to provide downward pressure to
keep the A/C head assembly in place as determined by the tilt and azimuth
screws and a pivot point underneath near the front. However, if it seems
loose, tighten it a few turns clockwise. This should not affect any of
the other settings.
If the problems happened suddenly, it is probably not a misadjusted audio/control head but some other mechanical fault - eliminate this possibility before considering A/C head adjustments. The following will attempt to get your mechanical settings back to something approaching normal even if the audio/control head was tweaked: I assume that you have cleaned it and replaced any dead rubber parts. I also assume that someone (we won't name anyone) has tweaked just about every mechanical adjustment. I would adjust the audio/control (A/C) head as best you can (don't touch this unless you know it was messed up by someone): * Play a tape that you know was recorded on a good machine. It may be easier to start with a tape recorded in SP mode since this is less critical. Once the basic alignment is complete, go back and fine tune with a tape recorded in EP. * Adjust the A/C tilt as vertical as you can by eye. If necessary, fine tune it for most stable tape movement - the tape should be at the same angle moving over takeup roller guide, A/C head, and adjacent fixed I guide. * Adjust the A/C height for loudest sound. At each end of the range of this adjustment, you will lose tracking/sync and tape speed may fluctuate (in addition to the sound becoming weak). * Adjust the A/C azimith for best treble (high frequency) sound. This is a precise adjustment - a 1/16 of a turn is significant. There will be a very small range over which the sounds will be clear and natural. A tape with music is best for making this adjustment. * With electronic tracking control centered, adjust A/C mechanical tracking (usually, a conical nut that moves the entire A/C assembly) until you get the least snow (if you have a picture at this point). Satisfactory tracking may be obtained at several positions of this control. However, only one will produce current video-audio sync. For the others, the words and the picture will be off by some multiple of 1/30th of second. * You may need to go back and touch up some of these again. There can still be other problems in the tape path including the height and angle of the roller guides and the height of the impedance roller assembly (on the left before or after the full erase head.)
You can do this by eye. Sophisticated test equipment and expensive test tapes are not needed. One trick is of course not to mess with both guide posts at the same time - but even if you do it isn't the end of the world. This doesn't even require a scope - the video picture is an excellent alignment tool! It does take patience and a steady hand. Also, have you touched any other mechanical adjustments - other guideposts, etc? Hope not. Also, I assume that any repairs to the guideposts have left them perfectly vertical - if they are tilted, then other tape path instabilities can result. The following checks and adjustments are made in PLAY mode. There is a ridge on the lower (stationary cylinder) on which the tape should ride - not above and not below. Play a tape that is in good condition and look closely at its bottom edge to see if it is sitting precisely on this ridge. If it is not, first verify that both roller guides are snug against the 'V-Stoppers' - the brackets at the end of the tracks where the roller guides stop in PLAY and REC. If they are not, then you need to determine what is binding or what has fallen off of the tape loading mechanism. See the section: "General tape path alignment problems". Assuming that the roller guides are correctly positioned on the tracks, the first step is to visually adjust the roller guides so that the tape just rides on that ridge on the lower cylinder. That ridge is a very critical part of the guide mechanism. There will be a set screw to lock each of the roller guideposts from turning. The appropriate one(s) will need to be loosened slightly - just enough to that the post is snug but can be turned by hand. The set screws may require a miniature metric hex wrench. Some just have a square head screw which can be loosened with a pair of needlenose pliers. Adjust each guidepost so that the tape just rides on top of the ridge. Now, for the fine adjustments. Which part of the picture is bad? * Left guide -> mostly problems with top of picture. * Right guide -> mostly problems with bottom of picture. Misadjustment can also cause a periodic loss of sync on a several second cycle. Make careful **small** adjustments of each one - then wait for a few seconds for any results to become apparent. Since the tape moves so slowly, it takes several seconds for the tape motion to stabilize to the new guide position. The left guide will affect the top part of the picture (mostly) and the right guide will affect the bottom. Once you are happy with SP, get a tape recorded on a known good deck in EP (SLP) mode since the tracks are narrower and fine tune it. Tape path alignment comments: 1. An EP recording requires the best tracking, and will thus make the best test source. (But it must have been recorded on a unit that was aligned properly). 2. Using forward and reverse search modes helps to narrow the adjustment. The guide height on the "feed" side for whichever direction you're going will have more affect. In other words, tweak one while searching forward, and the other while searching in reverse. 3. You could have the tape centered at the middle of the contact path, but too low at one end and too high at the other. 4. You could have the entire contact path too high or too low, and be in- advertently "correcting" by misadjusting the tracking control. You could be off by an entire track getting a good but very unstable picture since the ridge is not providing any guidance. Roller guide tilt: The roller guides (but not the fixed guide posts next to them) should be perfectly vertical. Sometimes there is an adjustment for this but usually not. Roller guide assemblies that have tilt due to wear will need to be replaced.
If it is impossible to find a position of the user tracking control that
results in a stable picture, this section is for you. Some amount of the
picture may be noisy - top or bottom - or the tracking may be fluctuating
with a few second cycle.
Mostly, these symptoms are related to problems with the roller guide
assemblies. (though electronic causes are also possible). The roller
guides are on the assemblies that move on curved tracks to wrap the
tape around the video head drum in play and record modes (and on newer
instant start VCRs, other times as well). Each roller guide assembly
includes a white cylindrical roller which should turn freely on a metal
guidepost, and a fixed guidepost at approximately a 20 degree angle.
1. Roller guides not fully engaged against 'V-Stoppers' (the metal brackets
at the end of the track on which the roller guide assemblies move when
entering PLAY or RECORD modes. Common causes:
* Obstruction or ridge on track preventing guides from completing their
movement. Visually inspect and observe behavior while entering and
leaving PLAY mode. Sometimes with use, an edge develops and the guide
gets hung up. A fine file can sometimes remove this.
* Parts have fallen off (don't laugh - JVCs tend to do this). Various parts
of the mechanical linkage that move the roller guides may loosen with
use and either fall off entirely or change position enough to prevent
full engagement. Compare left and right roller guide assemblies, they
are usually nearly identical in their operation and you should be able
to identify parts missing or out of position. These are usually on the
underside of the deck and will necessitate removing the bottom cover
(unplug the unit!). To gain access to critical parts of the linkage
which may be obscured by circuit boards or other components, you may
need to power the VCR, turn it on, press PLAY, and then pull the plug
just as the roller guides are in the middle of the track and accessible.
For the JVC problems, the parts are usually either a brass post or a
plastic link. The brass post can be glued back in place using a drop
of Epoxy. Make sure its shoulder is fully flush with the body of the
roller guide casting. For the plastic link, I have used a very small
screw to secure it in place from above. Some plastic cement may
work as well.
* Tracks on which roller guide assemblies slide are dirty and/or need
lubrication. Clean and grease.
* Obstructions such as toys or Cheerios blocking tracks.
Check the roller guides while the machine is playing a tape. They should be
firming pressed against the V-Stoppers. Any looseness indicates a problem
preventing full engagement. If pushing the offending guide into position
fixes the tracking problem, this confirms the diagnosis.
Note that in modes where the roller guides are retracted, the roller guide
assemblies are relatively loose and free to move. However, the amount
of movement possible should be similar for the left and right roller guides
and you should not be able to lift either entirely off of the track - the
ability to do so means missing parts underneath the deck. If the missing parts
can be located, they can usually be glued back into position.
Warning: if you find a roller guide assembly that can be lifted off the
track DO NOT attempt to load a tape - the floppy roller guide assembly
can smash into the spinning video heads ruining them - and your entire day.
2. One of the fixed guide posts next to roller guides (the ones that are
tilted about 20 degrees) have worked loose and fallen off. There should be
a tilted guide post next to each roller guide. If one is missing, it has
probably fallen into the machine. Immediately unplug (to avoid the
possibility of it jamming something and/or shorting components in the
electronics). Locate the escaped post - turn the unit upside down,
sideways, shake it, whatever until the loose post falls to the table
or floor. Glue it back into position with a drop of Epoxy or other
household cement.
3. The backtension band has come loose or broken. The backtension band
provides the force needed to keep the tape pressed against the video
and audio head. A backtension lever on the left side just as the tape
leaves the cassette is connected to a felt lined metal band that presses
against the edge of supply reel. The position of the level determines
the tension and is set up with mechanical feedback so that the tape tends
to move it against spring force just enough to provide the correct amount.
Test by moving the backtension lever a bit in each direction - you should
be able to observe the tension change. Backtension bands are easily
replaced. See section: "Backtension adjustment".
4. Mechanical damage due to trauma such as VCR falling off of TV. Cure, if
possible, will depend in extent and type of damage.
Most VCRs use a backtension band - a thin metal band with a felt liner - to apply a carefully controlled torque to the supply reel during forward tape motion in play, record, and CUE. A backtension lever or arm contacts the tape as it leaves the supply side of the cassette and provides feedback to control the tension on the backtension band and thus how much it resists the rotation of the supply reel. If the backtension is too low, poor tape-head drum contact results and you get a noisy intermittent picture. If the backtension is too high, there will be excessive head wear and in extreme cases, the drum will slow or stop entirely. Backtension is normally set using a special backtension gauge which you most likely do not have. If you own a TV with a vertical hold control, you can adjust backtension by setting the vertical hold so that you can view the head switching point - just above the vertical blanking bar. Above this point, you see the video from one head and below you see it from the other. When properly adjusted, these two segments should more-or-less line up. There are two adjustments for backtension: a spring position and the effective length of the band. To set the length, there is a setscrew which allows the end of the band to be moved back and forth. It is unlikely that you would need to set this unless you have just replaced a band or unmucked someone else's repair attempt. I usually consider the length to be correct when the angle that the tape makes going around the lever post is about 90-120 degrees. In other words, the tape should not be so tight as to not be deflected by the arm but should not be so loose as to be near or at the end of its possible travel. Then, set the spring force to align the picture above and below the head switching point. If you do not have access to vertical hold, you may be able to set backtension in the middle of the range where flag waving (see the section: "Flag waving - top portion of picture wiggling back and forth") is absent or minimized.
(From: Alan McKinnon (alan.mck@pixie.co.za)). Well, I'm about to open myself up to all sorts of scathing comments, but here goes: You can get by without a back tension meter. You will notice that just about every VCR ever made puts the back tension pole between a post and the impedance roller. Adjust the pole landing position so that it lines up with the middle of the impedance roller. Check your picture. If you have flagging at the top, or wavy lines, adjust the position. Fiddle it both ways to get the feel of it. Once you have experience, you can gauge the back tension by holding a screwdriver against the tape after it has passed over the full erase head. Your fingers are probably more accurate than most gauges anyway - I've never seen two give the same readings. My meter lies unused most of the time. I've lost count of the number of times I have chased around the VCR only to find my backtension meter was leading me astray.
(From: Paul Weber (webpa@aol.com)). The objective of the back tension adjustment is to prevent "flagging" which is horizontal displacement of scan lines at the top of the picture. You can use either B&W or color TV (or video monitor), provided that the unit has an accessible vertical hold (vertical sync) adjustment. You mis-adjust it until the picture rolls half-way and you can see the horizontal sync bar. This lets you see the very top of the picture (just below the bar). To make the adjustment, you need a known-good reference tape. You might trust a commercially-produced movie, but I'd recommend a real vcr alignment tape if you can find one. If you use a movie, then try four or five different ones to help insure you don't have one made on a defective machine. Adjust your machine so that vertical lines in the very top of the picture are as straight as possible. As to the specifics of what to adjust on your machine: You didn't mention the make or format of your machine, but I'll wager that the moving arm nearest the feed reel is attached to a felt-covered metal band (the brake) that wraps partially around the feed reel table. With tape loaded and moving, the arm balances tape tension applied by the drive system against tension supplied by a spring. If the tape tension becomes excessive, the brake is applied more; if the tape loosens, the brake is relaxed. Look at the attachment points for the spring attached to the arm. Usually, the back tension adjustment is at the chassis end of the spring. It may be an eccentric post than can be turned with a screw driver or a special tool, or it may be that you have to gently bend the tab. Either way, adjust the spring tension in very small increments, then observe the effect on the picture.
VHS cassettes use a clear leader and trailer for the purposes of detecting beginning or end of tape. A light source that pokes up in the center of the cassette illuminates photodetectors on either side of the cassette through passages in the plastic passing through the tape as it leaves and enters the cassette. The light source can fail - this is common on older VCRs where this was an incandescent lamp but rare on modern VCRs which use a special IR LED. The failure of this light source can produce a number of symptoms: * The VCR may simply shut down and refuse to do anything. VCRs with incandescent lamps often were able to figure out that the light bulb was burnt out since it was drawing no current and then shut down or flash an error code. * The VCR may go through the motions of playing a pre-recorded tape thinking that a tape is present because the sensors return signals indistinguishable from what it would see if a tape were present. Eventually, it may give up and probably shut off power. * The VCR may do strange things when you attempt to load a cassette since the microcontroller is receiving conflicting signals - the cassette is out but the sensors think otherwise. If your VCR uses an incandescent lamp and it is not lit when power is on, then the bulb is most likely burnt out. If either sensor fails open, then similar symptoms may result. If the sensor on the supply side fails shorted, then it will appear as though the tape is at the end. The VCR may refuse to play or FF or will attempt to rewind as soon as a cassette is inserted. If the sensor on the takeup side fails shorted, then it will appear as though the tape is at the beginning. The VCR may refuse to REW. In both cases, sometimes you can trick the VCR into cooperating and confirming that there is a sensor problem by pulling the connector for the appropriate sensor once the cassette is loaded. If you can get at the connectors, you can test the sensors by monitoring the voltage on the outputs. One test you might try if the VCR attempts to play an imaginary pre-recorded tape as soon as power is turned on is to locate the microswitch for record lockout protection - it will be located near the front (where the record protect tab would be once the cassette is loaded). Press this in while you turn power on. If the VCR now just initializes and displays cassette-in without trying to play, then it really thinks there is a cassette in place most likely due to a faulty sensor. In some cases, there could be other problems like a faulty mode switch or microcontroller producing symptoms that might be mistaken for faulty start/end sensors.
The start and end sensors are usually a combination of a light source (IR LED) and IR photodiode. With a little effort, these can be tested for functionality. * For an incandescent lamp (older VCRs), if it is not lit with VCR power on, it is most likely burnt out. Test with an ohmmeter. * For an IR emitter, an IR detector like the circuit provided elsewhere in this document or an IR detector card can be used to determine if the LED is operating. You can also try powering the LED with a low voltage supply and 500 ohm or so resistor using the IR detector to see if it works. Disconnect it from the circuitry first! Try both polarities to be sure you got it right. The sensors themselves can be tested by disconnecting them from the circuitry and shining an IR source on them (a remote control or incandescent bulb) while monitoring the resistance with a VOM or DMM. Use the polarity which give the higher reading (reverse bias). This resistance should drop dramatically if they are functional. If the start and end sensor assemblies are interchangeable, swapping them may be instructive. For example, this may shift the symptoms from play to rewind or vice versa.
There are two kinds of tape position counters: reference and real-time. What I call a reference counter is what all VCRs used up until a few years ago. A sensor counts revolutions of the takeup reel (usually) either directly or via a belt drive. A mechanical or electronic counter displays an arbitrary number which provides some idea of location. Since the rotation rate of the reel is not constant with respect to the actual time of the tape, it is not possible to use this for anything other than a reference. In addition, the tape may slip a bit and be wound tighter or looser depending on whether it was wound in play, FF, or REW. Thus, even the reference is not accurately repeatable. Failures can be caused by a broken or weak belt for the mechanically operated counter or defective circuitry for the electronic display. A failed sensor would most likely also cause the VCR to shut down and unload the tape as this is what is used to confirm that the takeup reel is rotating and that tape is not spilling into the bowels of the VCR. Real-time counters - which really are a vast improvement - operate off of the control track pulses from the control head. Tape location is measured in hours, minutes, and seconds though it is still relative and must be reset at the beginning of the tape if an absolute location is to be determined. The only disadvantages of real-time counters are that: * They do not operate with a new or bulk erased tape since there is no control track. Thus, it is not possible to leave a specific length section of such a tape unrecorded by using the counter to space over it. You must lay down a control track first by recording something - anything - for the time you want. However, it is advisable that this be a valid video source so that the sync pulses occur with the proper timing. * The tape must be in contact with the control head for all operations. In principle, this results in more head (and tape) wear though I know of no cases of the A/C head stack requiring replacement because of this design. Failure of the real-time counter on a VCR that otherwise works normally is quite unlikely and is probably an electronic problem since the control head must be functional for all record/play modes to work properly. However, it is possible that a failure of a half loading arm to fully extract the tape would result in problems in (non-search) FF or REW.
Reel rotation is detected most often using optical sensors under the reels though some older VCRs may use mechanical or optical interrupters driven off of belts from the reel spindles. * There will always be a takeup reel sensor - even on a VCR with a real-time counter. It has two functions: to (1) confirm that the reel is rotating and that tape is not spilling into the bowels of the machine and (2) to operate the (non-real-time) tape counter. Failure of this sensor will cause the machine to shutdown almost immediately and will result in a stuck tape counter. * Some VCRs will have a similar sensor on the supply reel. The output from this sensor can be used to confirm proper rotation of both reels both during modes involving tape motion as well as during the tape load and unload operations. Exactly when each is used will vary by design. If your VCR has identical sensors monitoring both reels, swapping the sensor assemblies may be instructive: the behavior will change if one is bad. For example, a VCR that would shut down in a couple of seconds in play mode may continue to operate correctly but now have problems with rewind. * Some fancier VCRs will display an estimate of tape remaining using the difference in rotation rates of the supply and takeup reels based on assumptions about tape thickness, hub size, and total length (which you may have to tell it). * Sometimes, reel rotation sensor problems are simply due to accumulated dirt on the reflective surfaces - clean them. In other cases, replacement sensors will be needed. While you are at it, replace both sides where appropriate - most of the cost to you is in your time, the cost of the sensors themselves is modest. Note that on VCRs with real-time counters, the real-time display as well as possibly the tape movement sensing operates off of the A/C head control pulses. Failure here could be due to dirt, a bad A/C head, tape path alignment problems, or failure of a half loading arm to properly extract the tape so that it contacts the A/C head.
The counters on some VCRs are active at all times - rotate the appropriate reel and the counter will change (count up or down depending on its default mode - the direction of rotation probably will not matter). If your VCR is of this type, testing is particularly easy. Slowly rotate the takeup (usually) reel by hand. The numbers should change several times - probably 4 - per revolution. There should be no missed counts and there should be no positions where the counter free runs - the display increments or decrements on its own very quickly. Any of these could indicate a problem with the sensor or LED, a buffer amplifier, bad connection, or the microcontroller or other IC that actually drives the counter and display. For electrical tests, first, locate the LED and photodiode. You can tell the difference by testing with a DMM on its diode test scale - the LED will have the higher forward voltage drop. Sometimes, the connections are even marked. What a concept! Momentarily touch and remove a resistor (1K ohms or so should work) across the sensor leads (while the VCR is in PLAY mode before it quits if needed). This should make the counter change if the the LED is bad or the photodiode is open. Alternately, a remote control may be able to activate it providing pulses that will look to the counter exactly like reel rotation. If this has no effect, unsolder the sensor (or unplug the sensor assembly from the main board if there is a connector) and try the resistor across the terminals where it was connected. If you now get a response, the sensor was shorted (or the connection was bad). If you do not get the counter to change in either case, there is a problem with an intermediate buffer amplifier, the electronics on the main board, or a bad connection leading to the main board. You will need to obtain the service manual or trace the circuit leading to where the sensor signal is detected. It is possible that the counter will only change when the microcomputer expects the reel to be moving, so a test while in STOP mode may not be valid. An alternative test is to use an ohmmeter across the photodiode on a high ohms scale. Use the polarity which gives the higher resistance and shine a light on the sensor. The resistance should drop dramatically with a bright incandescent light (these put out a good amount of IR). If it is infinite in both directions, the photodiode is open. If it is low in both directions, it is shorted. You may be able to make a measurement while the sensor is still in circuit, though other components may mask the resistance change. As noted, the IR sensor/LED combination is often a pluggable assembly. Using my VOM on a photosensor, I read infinite ohms with no light and 200 ohms with a bright light. However, your mileage may vary. If you have an oscilloscope, monitor the sensor output. If it is a voltage signal at this point (likely), then you should see it go high and low as you rotate the reel or shine light on it. With the reel rotation, the low and high periods should be roughly equal. There may be a buffer amplifier driven by the sensor - check its output as well. The signal there should be a cleaned up version (low pass filtered and possibly inverted) of the sensor output. In all cases, the signal should be a DC value without noticeable ripple or noise (block external light as fluorescent lamps in particular may add a 120 Hz ripple to your detected signal). Even at transitions between low and high or high and low, the level should change smoothly. You may be able to trace the signal to its final destination, the microcontroller or other large multilegged part, and monitor it there as well. Play a T120 tape recorded at EP speed near the end of the tape. This will result in the slowest takeup reel rotation. Or, if your VCR has the counter active in stop mode with the cassette out, rotate the takeup reel by hand very slowly. If the counter skips or 'free runs' at certain positions of the reel, there may be a problem with the hysteresis circuit. If this is external to the microcontroller, a resistor may have opened or there may be some other easily identified bad component. If it is internal to the microcontroller - either an actual circuit or firmware - then replacing the microcontroller may be the best solution unless you want to add your own circuit - I have done this to repair a Sears VCR with an erratic counter problem. It is a simple 1 or 2 transistor circuit (depending on what external circuits are already present). Monitor the sensor output when rewinding a T120 tape to the very end - this will be the worst case test as the pulses will be at the highest rate. There should be no missing pulses and the high and low times should still be similar. A bad sensor might result in unequal high and low times and dropped pulses at high speed.
(From: Stan Cramer (stvcrm@Gramercy.ios.com)). Try removing the take-up reel disk. Look on the bottom surface to see if there are a series of pie-shaped vanes - shiny, dark, shiny, dark, etc. If the shiny vanes get misted with smoke or general grak, the symptom is the same as if the sensor itself is faulty. Use some Windex or some such mild cleaner on the vanes and test the machine again. On some earlier machines, the take-reel disk might have a series of evenly spaced slots - blank,solid,blank,solid etc.-that interrupt the flow of IR light creating an electronic pulse stream. If your machine has this type of motion sensor, you can try brushing or blowing out the dust that may have accumulated in the small recesses surrounding the IR emitter and receiver devices on the sensor assembly. If these attempts don't do the trick, you probably have a faulty sensor.
There may be anywhere from 2 to 6 or more motors in your VCR. Some designs use a single motor to power all functions except the video head drum. Others have separate motors for each function. Most typical are 3 or 4 motors. Motors perform the following functions: 1. Cassette loading (front loaders only). 2. Tape loading (position tape around video head drum, etc.). 3. Video head drum rotation (servo controlled). 4. Capstan rotation (servo controlled). 5. Takeup reel rotation (PLAY, REC, FF, CUE). 6. Supply reel rotation (REW, REV). The video head drum (3) always has its own motor. It is internal to the lower cylinder or above the upper cylinder (except in the very oldest VCRs) and directly drives the spinning upper cylinder. Most consumer VCRs use a single motor for the capstan and the takeup and supply reels. Some also use this same motor for cassette and/or tape loading. Several possible types of small motors are typically used in VCRs: 1. Small brush-type permanent magnet (PM) DC motors similar to those found in small battery operated appliances, CD and tape players, and toys may be used for cassette loading and/or tape loading. 2. A similar but larger PM motor may provide power for the capstan and reel rotation and possibly multiple other functions (older VCRs). 3. A single low profile or 'pancake' brushless DC motor may provide power for a direct drive capstan, reel rotation, and possibly multiple other functions. 4. Brushless DC or 3 phase direct drive motors are usually used for the video head drum. Some of the very earliest VCRs used a belt drive for the video head drum.
Aside from obvious mechanical problems and lubrication if needed, you usually cannot do much to repair defective motors. If you enjoy a challenge, it is sometimes possible to disassemble, clean, and lubricate a motor to restore it to good health. However, without the circuit diagram, even knowing what the proper voltages and signals should be on (2) or (3) type motors would prove challenging. The following are some of the possible problems that can occur with the basic permanent magnet motors: * Open or shorted windings or windings shorted to case. * Partial short caused by dirt/muck or carbon buildup on commutator. * Burnt out armature due to defective driver, power supply, controller, or mechanical overload. * Dry/worn bearings. An open or shorted winding may result in a 'bad spot' - a position at which the motor may get stuck. Rotate the motor by hand a quarter turn and try it again. If it runs now either for a fraction of a turn or behaves normally, then replacement will probably be needed since it will get stuck at the same point at some point in the future. Check it with an ohmmeter. There should be a periodic variation in resistance as the rotor is turned having several cycles per revolution determined by the number of commutator segments used. Any extremely low reading may indicate a shorted winding. An unusually high reading may indicate an open winding or dirty commutator. Cleaning may help a motor with an open or short or dead spot but most likely it will need to be replaced. Note that unlike a CD player which uses some motors constantly, the small PM motors in VCRs are only used for loading operations and are generally quite reliable unless damaged by other problems. For more information on small PM motors, see the chapter: "Motors 101" in the document: "Notes on the Troubleshooting and Repair of Small Household Appliances and Power Tools".
Capstans are expensive especially if they are integral with the capstan motor, but unless it is bent (very unlikely), or the bearings are totally shot, or it is direct drive and the motor is bad, the capstan should not be a problem as long as you **carefully** clean off all of the black tape oxide buildup with alcohol and a lint free cloth or Q-tips. Don't get impatient and use anything sharp! The black stuff will come off. A fingernail may help. A dry bearing may need a drop or two of light oil (electric motor or sewing machine oil). Sometimes, there is a bearing cover washer that works its way up and interferes with the tape movement. Push it back down. Some Sony VCRs have had problems with defective capstan motors resulting in intermittent pausing or stopping of video playback when hot. The entire motor or just the bearing assembly needs to be replaced in this case.
From: whitmore@jila.colorado.edu (Mike Whitmore) VCR capstan motors are servo-controlled to allow precise speed and phase control. Typical signals are: VCC - power to chip/motor- probably 9-12V FG - frequency generator output from motor to servo loop CTL - control track pulse from Audio/Control head F/R - forward/reverse (one high, one low) There will probably be other connections for a variety of servo voltages, braking, grounds, etc. - You may need to find service literature for this VCR or the datasheet for the particular driver chip to get more info. Data will also tell if motor is 3-phase. This is common for many capstan motors and would require this IC to run it.
In order for the video to be read off of the tape properly, the spinning video heads must be centered on the very narrow diagonal tracks. The width of these tracks is as small as .019 mm. The actual reference point is not on the video heads but the A/C head - several inches away. The control pulses put down during record are used to phase lock the capstan to the spinning video heads. The distance between the control head and the video heads determines whether the required centering will be achieved. In the ideal world, the distance would be identical for all VHS VCRs - that is the goal. It is part of the VHS specification. However, whether from wear and tear, or even if the technician doing the setup in the VCR factory had an off day, this distance may not be quite identical on the VCR that the tape was recorded on and the machine being used for playback. Therefore, a way is needed to adjust the effective distance. A mechanical control would be possible but not very elegant. Therefore, an electronic tracking control is provided. This basically allows adjustment of the time delay or phase of the control pulses from the control head during playback. Record tracking is fixed. Actually, there may be as many as three tracking controls: (1) the user tracking knob or buttons, (2) an internal master tracking adjustment, and in fancier models, (3) an autotracking servo system. (Note: tracking is always automatically reset to the default when a cassette is inserted.)
A single pair (2) of heads is needed for basic record and playback. With more heads, various aspects of these functions can be optimized to improve picture quality - usually for the special effects like CUE and REV. For example, a 4 heads are usually needed to produce decent quality playback in CUE and REV modes for SP recorded tapes. Another set of heads is required for HiFi audio. The only possible difference for record or at normal playback speeds is in picture quality since with 4 or more heads, head widths/gaps can be better optimized for each speed. For example, a wide track width can be used at SP speed and a narrower one for EP speed. Which VCRs do this, I have no idea. In fact, such differences might only be visible to the average viewer in an A/B comparison under controlled conditions. The stability of the video playback has nothing to do with the number of heads. A jumping picture during playback is due to a servo system problem. With problems of this type particularly on a new VCR commercially recorded or rental tapes, it is more likely that the VCR is having problems with some kind of copy protection scheme.
The quick answer is: "almost any combination which includes at least one head of each azimuth angle on each side of the video drum" :-). For a 4 head VCR, this may even include all 4 at once. In this case, signals from both heads of the pair on each side of the drum are monitored and the one with the greatest amplitude is sent to the video circuitry. This provides clearer special effects for SP recorded tapes in particular - CUE, REV, SLOW, and PAUSE - where the video heads may be crossing tracks of both azimuth angles. Such an approach may be called a 'double azimuth' design by the manufacturer. For record and play modes, an opposing pair will be used but which pair will depend on speed - EP, LP, SP. Thus, almost anything is possible and it gets to be confusing very quickly! Don't count on finding this information in the service manual either.
(From: Paul Weber (webpa@aol.com)). A six head (VHS) vcr has 4 video heads and 2 audio heads on its rotating upper cylinder. The 2 audio heads record VHS Hi-Fi. They are about 1/3 the width of the most narrow video heads (about 6 microns). A four head machine lacks the audio heads and is therefore incapable of playing or recording Hi-Fi. There are also 2 head machines on the market. They use the same pair of video heads for all tape speeds. 4 and 6 head machines use the 28 micron wide heads for SP (highest speed), and the 19 micron heads for LP (middle) and EP or SLP (slowest) speed. Some machines have a 7th head: the flying erase head. It is about 40 microns wide, and when activated, can erase the recorded tracks of both video fields that make up a frame. Most vcrs use all 4 video heads to smooth out the picture when scanning in fast forward and rewind. This is why 2 head machines have much more noise in the picture when scanning. Machines that have a switch to turn off the 19 micron heads do so in an attempt to improve the playback of tapes made on old 2-speed (SP and LP) machines. These machine had video heads that were something like 22 microns wide, and scanning them the narrower heads of a modern machine sometimes produces unacceptable results. Compatibility problems between machines are a fact of life because of mechanical differences. Recording at the highest possible speed minimizes problems, but hi-fi audio tracking problems can happen even then because the tracks are so narrow. If you have video tracking problems between 4 and 6 head machines on tapes recorded at the highest speed, it is because of mechanical differences, not because of the number of heads on the machine; the number of video heads is identical. The differences are in the alignment of the audio/control head that controls synchronization of the video upper cylinder, and in alignment of the video heads themselves.
SVHS won't be better than a good 4 head (+2 HiFi) unless: 1. You use high quality (read: expensive) SVHS type tapes (usually, there may be exceptions and some people claim that premium VHS tapes will work for SVHS recordings if the proper hole is drilled in the case but don't count on it). 2. The recordings are actually made in SVHS mode. 3. They are played back on another SVHS deck. Since few people have SVHS decks, there is probably little benefit if the objective to to make high quality recordings to share. I would probably go with a good 6 head (including 2 HiFi) since it will be compatible with everyone. However, just saying it has 4 or 6 or 25 heads doesn't mean it will produce a high quality result - there is a lot of variation in video and to some extent HiFi audio quality.
I assume VISS stands for "VHS Index Search System" or something similar. In any case, VISS and VASS provide the means to mark the start (usually of a video segment so that it can be accessed quickly later on. "How standard is this system? My Goldstar VCR has VISS and now I see reference to an LXI brand with the same system. I've heard of other VCRs with functionally similar features, but never had the opportunity to try exchanging tapes. Do they use the same marks? When my Goldstar finally bites the bullet (beyond my powers to resuscitate it), will the collection of indexed tapes I've built up be useless, or will another VCR with indexing features find the marks that Goldstar put on them?" (From: Ed Ellers (kd4awq@iname.com)). VISS is a real standard, issued by JVC in 1986. There is also a VASS -- VHS Address Search System -- using the same techniques, but it was taken off the market in 1988 after a patent infringement suit by a German company; JVC settled that case, but VASS never came back (at least not in North America); JVC later developed a more sophisticated system called CTL Coding, but it's not used on consumer VCRs over here either. VASS records four-digit codes instead of a single index mark; CTL coding records an actual time code on the control track, and also provides for VISS and VASS use. Incidentally, VISS and VASS work by altering the duty cycle of the 29.97 Hz square wave recorded on the control track; the servos still work on the average phase of the signal, but the changes in duty cycle are decoded into a slow bit stream. Before VISS was developed a number of VHS VCRs had a different indexing system that recorded a low-frequency signal across the entire tape, using a special head on an arm that contacted the tape while it was rewound into the cassette; these index codes could only be placed at the beginning of a recording and couldn't (then) be read except during rewind and fast forward modes. Theoretically a modern VCR could be made to read this signal using the control head, but this would require a special circuit to be added; I don't know of any VISS-capable decks that can do this, and given the small number of recordings likely to still exist with the old index signal it wouldn't seem to be worth the trouble.
(From: Matt Kruckeberg (sackmans@ndak.net)). My understanding of commercial advance is that the program is monitored during recording for fade to black and silent audio between programming and commercials and between commercials. The microprocessor stores these events in memory until the recording session is over. It then analyzes these events to determine whether an event was part of a group of commercials or just a dark silent passage of programming. The tape is then rewound and the beginning and end of the commercial groups are marked with special start and end signals recorded on the control track, similar to index search marks. During playback with the feature activated the unit will automatically forward search when a start signal is detected and resume normal play when an end signal is detected.
It always amuses me to listen to comments about how anything older than 6 months (or 30 minutes) should be tossed in favor of some newer, more cheaply made piece of crap. Yes, convenience features and HiFi audio have made newer VCRs a lot nicer in many ways. But for time shifting and the kids, that old clunker will do just fine, thank you. Some of the older VCRs will just keep going and going and going and going with a cleaning and a few rubber parts from time-to-time. On the other hand, I had to repair my high-end (for 1990) moderately used Mitsubishi VCR because a 10 cent plastic part broke (their cost, my cost - $10) - clearly an exercise in design-to-fail engineering. For about .5 cents more, it could have been built never to fail. The replacement part was identical to the original, so I give it about 4 years.
(From: Stan Cramer (stvcrm@Gramercy.ios.com)). In recent years, the rapid decline in the quality of construction of VCR's has been widely chronicled here and in other forums. Through all of this criticism, I have staunchly defended JVC as the last bastion of construction integrity! Alas - no more! Tonight, I had the occasion to open up a JVC HR-J620U and was shocked at what I saw! I am sad to announce that even the once venerable JVC has sold out to the concept of making machines really light and really, really crummy! This new JVC transport is the epitome of designing "throw away" machines - even worse than the transports offered by Matsushita or Funai! Glaringly absent is the modular power supply. You may no longer fall back on the last resort - replace the power supply! Folks, this is just an unmitigated piece of unadultered crap! As both a consumer and a VCR technician, I am truly offended by the shoddy construction of all new VCR transports and, in particular, by the caving in of JVC to make machines geared to the lowest common denominator. All of us should be outraged! (From: Greg Monbourquette (gregm@globalserve.net)). I too am concerned about the lack of care that the engineers who put these things together take when considering the amount disassembly required in order to only clean a lousy belt. (I'm talking mostly about the RCA/GE models with a plastic plate covering the bottom of the VCR) And yes there was once a time when you could buy/sell a vcr and KNOW that the customer won't have any problems for at least 5 years . I tell my customers all the time when they finally decide that the 15 year old TV that finally died ( for the first time) will be replaced by a new one, " don't expect 15 years out of any TV you buy today. Oh well we've (I've) ranted long enough. I now know my feelings aren't only mine.
Possibly, but why bother? You will most likely be limited by the VCR's circuitry anyhow. All S-Video means is (1) a special connector and (2) separate luminance (Y) and chrominance (C) rather than composite video. In a VCR, you will need to bypass the input circuitry and get to the place where Y and C are separate. This may or may not be possible depending on its design. It is probably not worth it as you will likely not gain much in picture quality but if you really are determined, a schematic will be essential. If all you want to do is allow for an S-video input, there are single chips which will combine the Y and C into a normal composite video signal.
It would be nice if it were possible to output still frames from a PC, for example, to record computer animation on video tape. This would permit images to be generated slowly and then played back in real-time. However, there are a couple of problems with attempting to cleaning record single frames on a consumer grade VCR: * Without moving the tape, only a single field (of the two interlaced fields in a video frame) can be recorded since the tracks for the A and B heads will be superimposed. I doubt that any VCR not specifically designed for single frame recording has any support for moving the tape in this manner. * The control and synchronization circuitry to cleanly switch the record for a single frame may not exist. This will depend on the model - the more sophisticated the editing functions that are supported, the more likely that this precision will be supported. * The VCR must have a flying erase head or you must use new or pre-erased tapes to avoid the rainbow interference on the first few hundred frames of any recording made over old video. Other than that, there is no reason that the video writing circuitry cannot be turned on during pause - some VCRs will do this if you go into record mode while in pause. Obviously, anything you can do from the front panel or remote you can do under computer control. There could be hidden functions accessible via a special connector or key sequence but you would need documentation for your unit which may not be readily available, if at all.
Here is one approach to using a PC to program multiple VCRs. Obviously,
the techniques described below can be extended to more complex functions.
Feedback could be added to inform the PC of end-of-tape or other fault
conditions.
(From: Bill Mohler (bill@cs.oberlin.edu)).
We did a project to control multiple VHS VCRs where time and cost
were major factors. Our VCR's were the same brand (assorted models with
same IR codes), so we hacked a remote to interface to a PC's parallel port.
The basic idea was to have the PC select a VCR then "push" a button for
function.
The remote hack was simply an analog switch (TTL input) across the switch
contacts and a 754XX peripheral driver to select an IR LED mounted right
in front of each VCR's IR window.
The software was simple. We only needed 4 VCR's and 4 functions, so we
split the 8-bit printer output into two 4-bit commands ("VCR select" and
"function") and "poked" away. Not bad for a days work.
You could use decoders or the printer control port to get the extra "bits"
you need.
Some VCRs and TVs may have a selector switch or be universal but you would have to check the manual. Power wise using a transformer will probably be fine. The power line frequency is not used for anything in the TV or VCR except possibly the clock on the VCR which will run slow or fast. Standards differ and you won't be able to watch or record broadcasts/cable unless your equipment supports multiple standards.
The only difference between using a blank tape purchased in the US then used in the UK is the playing time will be different ie, a T120 (2 hours) from the US will have a longer playing/record time in the UK. This is due to the different head drum speed i.e., 60 Hz (1800 RPM) and 50 Hz (1500 RPM).
A VCR is not simply 'analog playback' in the same way that an audio recorder doesn't care whether you record classical or rock. The VCR must synchronize to the video timing and demodulate the luminance and chrominance information in order to lay down the tracks on the videotape. There are enough differences among world video formats that while technically possible (and such multiformat VCRs exist) it is not automatic - or free. The video timing and modulation techniques for video formats like NTSC, PAL, SECAM, etc. are sufficiently different that additional circuitry is necessary to handle multiple formats. In the U.S. at least, there is not enough demand to justify the added expense. The technology of video recording makes interesting reading and the sophistication of the circuitry and mechanism of a $200 VCR is quite amazing. TVs are more likely to accommodate difference standards than VCRs. Even a regular TV may be able to be used to play from a different standards VCR. For example, NTSC 30/525 and PAL 25/625 use very similar horizontal frequencies but different vertical rates and color encoding. Playback will be possible (in B/W at least) if the vertical lock circuitry (or the vertical hold control if there is one) on the TV has enough range. A simple color code converter can then be easily constructed using a couple of chips and some discrete parts.
The use of a $2 T120 tape with a HiFi VCR permits the recording of up to 2 hours of audio with near-CD quality. However, some designs require a video input to stabilize the drum speed and possible degradation (e.g., wow and flutter, noise, etc.) of the recorded audio. Some VCRs will work fine without any video. Others need it to stabilize the drum speed from the vertical sync. For best results of audio-only recording, find a source of video-black such as a camcorder with the lens cap on to minimize possible video interference (though this is usually not a problem).
(From: Mike Appenzeller (Michael.W.Appenzeller@lmco.com)). I don't think any stereo modulators exist, other than very expensive professional models. The processing for TV stereo sound is much more complex than FM stereo, involving dbx companding/NR on the L-R difference signal. Hi-Fi VCRs mix the two audio channels together before feeding a mono-audio modulator. I laugh at all the people who buy a Stereo TV, HiFi Stereo VCR, then insist on using the Channel 3/4 VCR RF outputs instead of the direct A/V connections. They are getting MONO Sound!
"Is it possible to rerecord the video (and linear audio) tracks but preserve the HiFi audio?" You cannot do this without disabling the erase head(s). If this is done, you will get interference from the previously recorded video - the rainbow patterns present at the beginning of recordings over old material on VCRs without flying erase heads. Even if it were possible, I don't know how robust writing over the HiFi audio tracks would be - you might get degradation after 1 or 2 dubs.
Some VCRs do not have much of a long term memory should there be a power failure. Can a UPS designed for a computer system be used with these VCRs so that all the programming (and possibly channel settings as well) are not lost every time the power line burps? A UPS might be a solution but there are some issues to keep in mind: * If your VCR uses a switching power supply (with no input power transformer), it may be fine as the waveform does not matter that much. If it uses a power transformer, then there could be problems if the waveform put out by the UPS is far from sinusoidal - which it likely is. * The VCR is a very light load. I don't know if this could be a problem with some UPSs. * The inverter in a typical UPS may generate Radio Frequency Interference (RFI) but this probably doesn't matter if it only runs when the power fails and you aren't viewing or recording at the time. If your VCR recently developed this amnesia, then you might consider attempting to locate the cause (a shorted NiCd backup battery or bad supercap) and correcting it rather than tying up a UPS for this purpose.
The answer is yes but I would not recommend it. In order to provide reliable backup, totally error free storage and retrieval must be guaranteed. This is a non-trivial problem given that the video tape is an analog storage media prone to noise and dropouts. Redundant information would need to be stored and sophisticated error detection and correction circuitry must be included. By the time you are done, the theoretical capacity of a T120 video cassette of, perhaps, 5-10 GB is greatly reduced. Furthermore, you probably want somewhat rapid random access and this **will** be very hard on a consumer grade tape transport designed for movie viewing and time shifting of soaps. With the cost of reliable tape and disk storage units having enough capacity to backup a 1 GB hard drive available or on the way for less than $200, it doesn't make sense to use a VCR with a totally incompatible format and questionable reliability when you will need it most - in a data emergency. I have no idea if the following is any good - I kind of doubt it - but various products of this type were developed before devices like cartridge tape (and now the Zip(tm) drive) backup became popular. (From: Robin Gilham (gilham@stb.dfs.co.za)). I saw an ad for a plug in card and software only yesterday, claiming 2G of storage on a 240 minute VHS tape. Wait.... yes, here it is. The product is called "BACKER", and in .nl available from Timtronics (+31-50-314 0937). Comes with interface card and Windoze software, will backup harddisks at speeds of up to 9MB per minute for DFL159 (which is less than US$100). (From: then@superpallo.cs.hut.fi (Tomi Holger Engdahl)). The manufacturer of BACKER is Danmere Technologies Ltd and they have WWW-pages at http://www.danmere.com/. What they claim by 9 MB per minute, that is the data rate at the maximum speed, maximum compression and minimum error correction. The uncompressed data rate is 5 MB per minute at highest speed. (From: Karl-Henrik Ryden (kalle@pobox.com)). I have one of their cards. It works, but is rather tedious to use. It is kind of like in the old ZXSpectrum/VIC64 days. :-)
First, you might be able to repair the VCR and prolong its life. Why are you reading this section and considering such a transgression? Grrrr. OK, so you really want to just use its timer. There are two things you would have to do: 1. Trick the transport into thinking there is a recordable tape in place. This is not hard - an old cassette shell will probably be all you need for this. Then you don't have to worry about your non-recorded tape from running out or wearing out. 2. Find a signal that can be used to control a relay, solid state relay, or optoisolated triac. If you are electronically inclined, this should not be too hard. If nothing else, the record LED or any switched power bus would suffice. A solid state relay or optoisolated triac takes a logic signal and will control a resistive AC load. Check the specifications if you want to control some other type of load like a motor or external tape deck. A suitably rated normal relay could also be used but a driver circuit may be needed to power the coil. Some (rare) VCRs have a switched outlet in which case this is trivial.
Perhaps, you have this fantasy: "I'm wondering if it's possible to take the tuning circuit (tuner and associated circuitry) out of a VCR and somehow controlling it with a PC (say through the parallel port), and then feeding the composite signal to the input of a video capture card?" If removed from the VCR, you will need the complete specs on the digital interface between the VCR's system controller and the tuner (assuming it isn't on of those old types selected by mechanical switches!), as well a substitute power supply. This information may not be available even if you purchase the complete service manual. However, you may be able to infer it by monitoring the relevant signals with an oscilloscope or logic analyzer :-). An easier approach may be to use the entire VCR intact and interface via the front panel (by simulating the Chan +/-, TV/VCR, etc. buttons) or via IR by simulating its remote control.
The question you originally asked might have been: What is this alien looking thing in my VCR? The object in question may look like a pentagonal shaped frosted glass slab with two pairs of wires sticking out of adjacent edges. What it is, is an acoustic delay line implementing a one TV line (1H) delay - around 63 microseconds (NTSC). The crystal is a shaped cavity and the polished edges are acoustic reflectors. There are a pair of piezoelectric transducers - one to launch a wave and the other to pick it up. The acoustic waves bounce around in a zig-zag pattern which increases the effective path length, thus the unusual shape. Uses in a VCR include a comb filter and tape dropout masking. The comb filter is part of the chroma circuitry and computes the sum of the current and previous video lines during recording and playback. The acoustic delay line therefore implements a delay of exactly one horizontal line. Due to the various games that are played with chroma signal phase in the NTSC-VHS system (as well as BETA and PAL), the end result is that chroma signal amplitude is doubled and crosstalk between adjacent tracks is canceled out. This is because the chroma signal is always exactly in phase between successive video lines but the crosstalk between adjacent tracks is always exactly out of phase. The name 'comb filter' is derived from the shape of the frequency response of the comb filter - its evenly spaced spikes look somewhat like a hair comb and it is used to 'come out' the crosstalk components of the chroma signal. Another use for am acoustic delay line is dropout masking. The surface of the tape is not always perfect - bits of oxide fall off or slight dips or bumps result in momentary loss of head-tape contact. One way to minimize visible streaks in the video is to replace the lost signal with video from the previous scan line. Nothing alien about it, just not your everyday electronic part.
