Contents:
Notes on the Troubleshooting and Repair of Video Cassette Recorders
Copyright (c) 1994, 1995, 1996, 1997, 1998
All Rights Reserved
Reproduction of this document in whole or in part is permitted if both of the following conditions are satisfied:
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 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 pla