Notes on VCR Failure Diagnosis and Repair V1.01

• 1) About the Author
• 2) Safety
• 3) Parts of the Tape Transport in a VCR
• 4) Most common problems
• 5) General Guide to VCR Cleaning and Rubber Parts Replacement
• 6) Parts Sources
• 7) Tape Eating
• 8) Erratic Behavior in Various Modes
• 9) Mechanical Relationships in VCRs
• 10) Bad Sound Quality on Non-HiFi VCR
• 11) Bad quality sound from HiFi VCR
• 12) Tape Gets Crinkled and/or random switching between speeds
• 13) What is a video head?
• 14) Is your video head really bad?
• 15) Video Head Cleaning
• 16) Where to obtain replacement video heads
• 17) Replacement Technique
• 18) Capstan problems
• 19) Power supply problems
• 20) Flameproof Resistors in Switch Mode Power Supplies
• 21) Tape sticks to head drum
• 22) RF signal problems
• 23) The VCR is failing the Power-up sequence
• 24) Interference as parallel horizontal lines when playing tape
• 25) Snow on one or more speeds
• 26) VCR will not go into play or record or aborts before fully loading tape
• 27) Sudden problems with tracking/snow on part of picture
• 28) Roller Guide alignment
• 29) Likely causes for sudden change in tracking behavior
• 30) Revival of Dead Remote Control Units
• 31) Why is a Special VCR Needed for International Video Standards?
• 32) Symphonic/Funai brand vcr won't rewind or fast forward
• 33) IR Detector Circuit

My apologies to anyone whose info was included here without proper acknowledgment. I will be happy to add references if you email me.

Author: Samuel M. Goldwasser
Corrections/suggestions: sam@stdavids.picker.com
Copyright (c) 1994, 1995
All Rights Reserved

Reproduction of this document in whole or in part is permitted if both of the following conditions are satisfied:

1. This notice is included in its entirety at the beginning.
2. There is no charge except to cover the costs of copying.

Other precautions:

• Don't wear any jewelry or other articles that could accidentally contact circuitry and conduct current, or get caught in moving parts.
• 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.
• 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.
• 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.
• 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 accidently connect it to a live circuit.
• 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!

Supply reel

Left hand side platform on which the supply tape spool sits. Edge which contacts idler tire should be cleaned.

Takeup reel

Right hand side platform on which the takeup tape spool sits. Edge which contacts idler tire 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.

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.

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. 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. Clean and inspect.

Video head drum

Almost 3 inch diameter by 3/4" high contains the video heads (and HiFi audio and flying erase heads, if present). Stay away from this unit - 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, may 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 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. A hard, shiny, dried out pinch roller can lead to tape edge munching and erratic sound/speed/tracking. Clean thoroughly. Inspect for cracked or deteriorated rubber.

Audio/Control Head assembly

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 band and serves to maintain a constant tension on the tape during play, record, and forward search. Retracts toward cassette when tape is unloaded. Backtension is somewhat critical and may need adjustment after long use.

Various other guide posts

Vertical stationary metal posts which tape contacts. Should be cleaned but rarely need adjustment.

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. Clean.

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. These will need replacement after a few years. Clean and inspect.

• 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.

Do not attempt to clean the video heads until you read the procedure below, 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.

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 Qtips 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 Qtips 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 below. 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.
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. 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 Qtips 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 Qtip 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.

   On some models, you may need to unscrew circuit board(s) blocking access to either the top or bottom of the tape transport.

   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.

   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) leave the video heads alone.

   I have used wet type cleaning head cleaning tapes with some success. Follow the directions but wait sufficient time for everything to dry out or you will have a tangled mess - 15 minutes or so should do it..

   To clean by hand, you will need what are called 'head cleaning sticks'. These are covered by chamois and are safest. DO NOT USE QTIPS (COTTON SWABS). These can catch on the ferrite cores and damage them or leave fibers stuck in the heads. Qtips can be used for cleaning the other parts like the rollers and audio/control head as described above but not video heads.

   To use the cleaning stick, moisten it with head cleaner or alcohol. Pure isopropyl is best, however, the 91% medicinal stuff is OK as long as you dry everything pretty quickly. Don't flood it as it will take a long time to dry and you run the risk of any water in the alcohol sitting on surfaces and resulting in rust (very unlikely, but don't take the chance).

   Gently hold the flat portion of the chamois against the upper cylinder where it is joined to the lower (non-rotating) cylinder. Rotate the upper cylinder be hand so that the heads brush up against the moist chamois. DO NOT MOVE THE HEAD CLEANING STICK UP AND DOWN - you will break the fragile ferrite of the heads - $$$$. Side to side is OK as long as you are gentle.

   I know people who use moistened typing paper or even their thumb for this but I would not recommend it as a general service procedure!

   Depending on how dirty your heads are, a couple of passes may be enough. Let everything dry out for at least 1/2 hour. This process can be repeated. However, one pass will usually do it.

MCM Electronics @ 1-800-543-4330

VCR parts, Japanese semiconductors, tools, test equipment, audio, consumer electronics including microwave oven parts and electric range elements, etc.

Dalbani @ 1-800-325-2264

Excellent Japanese semiconductor source, VCR parts, other consumer electronics, etc.

Premium Parts @ 1-800-558-9572

Very complete VCR parts, some tools, adapter cables, other replacement parts, etc.

First, eliminate the possible mechanical causes such as slipping belts or a bad idler tire. Another possibility is that a sensor assembly present on many VCRs called the Mode Switch is dirty or bad. The purpose of the Mode Switch is to inform the microcontroller of the gross position of the mechanism at all times. For example, the mode switch may have 4 positions:

1. Tape unloaded and cassette out.
2. Tape unloaded and cassette in.
3. Tape half loaded around drum.
4. Tape fully loaded around drum.

Modes Switches may or may not be easily accessible. On some, they are visible once the bottom cover is removed. On others, they are buried beneath a bunch of mechanical dohickies (technical term). Some come apart with a screw or two and a connector. Others require desoldering and the removal of a whole lot of stuff.

Once, you get at them, you can often snap apart the housing and use contact cleaner/lubricant on the sliding contacts and surfaces.

However, be very careful about not moving anything and take careful notes on the position of any parts that you disconnect as critical timing relationships are controlled by the gear positions. See the section below on 'How not to mess up your day my ignoring timing marks' or more simply: Mechanical Relationships in VCRs'.

1. The audio head needs to be cleaned. A cleaning tape may not be effective. You can use Q-tips and medicinal or pure isopropyl alcohol or tape head cleaning solution. Might as well clean the tape guides as well while you are at it - a speck of dirt can cause the tape to wander and produce erratic sound.
2. The audio/control head needs to be aligned - particularly the azimuth adjustment which is the angle the head gap makes with respect to the direction of the tape's long axis (I hope this is clear). You can do this if you are so inclined. Before you adjust azimuth, a test for this would be to record and then play back a tape on this machine - regardless of how far off the azimuth adjustment is, the recording should sound good (at least as good as one can expect from SLP linear audio). See section on tape path alignment.
3. The audio head (and other parts) needs to be demagnetized - use an audio tape head demagnetizer. Stay away from the video heads. Some demagnetizers are powerful enough to damage them. Make sure the demagnetizer you use has a no sharp ends to damage anything - cover with electrical tape if in doubt. Turn on the demagnitizer and move it slowly near all metallic parts that the tape contacts - guides, levers, erase and audio/control head. As mentioned, do not go near the video heads.
4. The audio head is worn. If the poor sounds quality really bugs you, these can be easily replaced but they are not cheap since generic replacements are rarely available. It will then need to be aligned.
5. Tape path problem causing bad tape-head contact. See section on tape path alignment.
6. Your expectations for audio quality on the linear audio tracks on a non-HiFi VCR are unrealistic. The worst will be a stereo VCR in EP mode since the stereo tracks are less than half as wide as non-stereo tracks. Best will be SP non-stereo but even this is very poor for music. Once you get used to HiFi quality, linear audio sounds like crud.

What to look for if it is really playing HiFi (try at slowest tape speed as this will have little effect on HiFi quality but will turn the linear track quality to crud):

• Almost no added tape hiss.
• Excellent high frequencies - again almost the same as the original.
• Excellent dynamic range.
• No detectable wow or flutter - use a music source.

It could be the guide posts or other tape path components, but before you turn every screw you can find and make the problems hopelessly worse, replace all of the rubber parts - belts, idler tire, pinch roller. And while you are at it, give the machine a good cleaning.

If you want to do this before buying the new rubber (which BTW should not be more than a total $10-$15 from a place like MCM Electronics), you may at least see a temporary improvement in performance.

You really need to determine exactly where the tape is being crinkled. Once you do this, you may be able to determine the cause and visually verify whether the problem is effected by any adjustments or probing you do.

Some possibilities are:

• Worn feet on the roller guides causing them to not be precisely vertical. Sometimes there are adjustments for tilt; usually there are none. Sometimes replacements are readily available (especially if this is a common problem with your model).
• Cassette not seating properly. Press down on cassette while playing a known good tape. If it moves, then check for obstructions or foreign objects such as toys or peanut butter and jelly sandwiches! A dirty, oily, or just tired belt may not grip well enough for the mechanism to complete the cassette load cycle.
• Various guides too high or too low but this is pretty unlikely unless they have loosened somehow.

The heads themselves are made from ferrite which is an extremely hard ceramic magnetic material which is also very fragile. The head chips can be seen at the very bottom of the rotating upper cylinder. The actual construction is of a 'C' shape with a very small gap between the arms of the 'C' - about 1 um or so. This is filled with with a non-magnetic material to force the magnetic field out of the head into the tape and to prevent material from collecting in the gap. A few turns of fine wire form the coil of an electromagnet for recording and as a pickup coil for playback. If you look at a head chip from below (on a cylinder that has been removed) you can see the coil and the shape of the core, though you will not be able to tell if a head is bad or worn by this inspection unless there is obvious damage). A powerful microscope is needed to even see the gap.

Indications of a bad video head include:

• Any visible damage to the ferrite chips. Heads nearly always appear in opposing pairs on the upper cylinder (head drum). Any visible discrepancy between the chips in a pair is probably damage. Sometimes 1/2 of the core breaks off leaving the windings dangling. Common causes for this damage are improper cleaning techniques or the use of damaged or spliced tapes. Use a magnifying glass and bright light to examine the heads but do not touch! By the way - improper splicing of broken video tapes is a good way to break video heads. Any kind of splicing should be avoided if at all possible.
• Excessive video snow which cannot be eliminated by the tracking controls. An image where more or less good video alternates with snow at a 30 Hz rate means that one of the 2 heads in a pair is either dirty or bad.
• Excessive video snow or no picture on some playback speeds (SP, LP, EP, still) since different sets of heads (in 4 head or more) machines are often used for different speeds. If this is due to wear, then it would probably gradually deteriorate and not happen suddenly.
• Inability of certain internal adjustments such as backtension to eliminate erratic tracking problems may indicate a worn video head.
• You have just been playing a rental, damaged, or spiced tape and you notice any of the above symptoms.

Advanced: To check the signal from the heads I would suggest you need a circuit diagram so that you can locate the relevant test points and expected FM voltage levels in the head preamp. This will be housed in a metal enclosure, usually right next to the head assembly (at the rear). I guess this should be done with an alignment tape, but I've found any known good recording should provide a reasonable approximation.

Other basic checks such as visual check with a magnifying glass, continuity tests on the heads as well as power supply voltages in the preamp can also help. (Richard Szewczyk)

VCRs should be cleaned periodically, but video heads usually do not need periodic cleaning as the spinning head performs a self cleaning function.

If you insist on cleaning the video heads, refer to the section on general cleaning and rubber replacement.

Electronics suppliers such as MCM Electronics, Premium Parts, and Dalbani stock a wide range of video heads for VCRs that are more than a couple of years old. (They may not have heads for the latest models.) In some cases, they will offer two kinds of heads for the same model - a generic version and a 'name brand'. Unless you are extremely critical, there is probably no need to spend the extra on the 'name brand' head. There is also no need to pay the premium charged by the original manufacturer of your VCR - it is often priced 2:1 or more over what a generic head will cost with no substantial difference in performance, if any. You may even end up with exactly the same head manufactured on the same assembly line!

Note that currently, the price of many upper cylinders (video heads) for 2 head VCRs is well under $25 so ordering a replacement may be a better investment of time and money than a long diagnostic procedure.

1. Do not touch the actual video head chips themselves. Handle the head as little possible. You can touch the upper part of the head cylinder if necessary. One thumb through the center hole with fingers resting on the upper edges works pretty well.
2. Before you unmount the old one, mark or make a note as to its position - sometimes it is possible to mount the new head 180 degrees off from way it is supposed to be oriented causing tracking problems at the least as the opposing heads are not identical. (The azimuth angles are +/- 6 degrees for VHS).
3. Unsolder the connections between the head and the upper cylinder. There will be 2n solder connections for an n head VCR. (Sometimes there is some kind of connector rather than solder connections, but this is rare.) Examining the new head should reveal exactly where to unsolder. For pins through the printed wiring board type, you should use some kind of desoldering tool - solder pump, SolderWick, or a vacuum rework station.
4. Unscrew the 2 or 4 Philips head screws holding the old head in place. It should be obvious from the new head which screws need to be removed. You may need to remove the static brush if your VCR has one or some other usually obvious stuff to get at it. DO NOT touch any other screws on the head drum as these are critical adjustments one should not mess with.
5. Lift the old head straight up and off. You should not need to use any drastic measures though a little jiggling may help. I have never actually needed a head puller.
6. Replace in reverse order, solder the connections, replace any other hardware that was removed. Refer to your notes on the position of the old head and/or the color codes (wire colors, dabs of paint, etc.) as to orientation on the drum.
7. Carefully clean any fingerprints from parts of the head drum you touched. Again, do not touch the video head chips themselves. You may use 91% medicinal alcohol, though pure isopropyl is preferred. Avoid rubbing alcohol especially if it contains any additives. Let the machine dry completely.
8. Unless you tweaked any mechanical adjustments, the VCR should work fine assuming the video head was the problem. If the tracking is way off, refer to your diagram and double check that you didn't replace the head rotated 180 degrees from the proper position by accident.

A power strip with a circuit breaker, even with surge protectors is not a reliable protection against power surges especially during lightning storms. The only sure protection is unplugging electronic equipment during storms.

There are usually half a dozen different voltages used within a VCR - if one of these dies, some portions will work but will not receive the proper signals from the dead parts. So, nearly any kind of behavior is possible.

Power supply problems in VCRs are among the easier electronic problems to fix. Two very common types of power supplies in VCRs are:

1. Power transformer with multi-output hybrid regulator. These regulators fail quite often with one or more outputs dead or low. It takes about 5 minutes with a voltmeter and ECG cross reference to locate the bad output and decide to replace the regulator. Typical part is STK5481 - a black box about 2"x1.5", approximately $12.
2. Switching supplies. These are tougher to diagnose, but it is possible without service literature by tracing the circuit and checking for bad semiconductors with an ohmmeter. Common problems - dried up capacitors, shorted semiconductors, and bad solder joints. In a supply that is dead - has blown the main fuse - check **all** semiconductors, capacitors, and resistors as a failure in one may damage others and just replacing the first one you find that is bad may result in it just blowing immediately. Fusable (flameproof) resistors (blue or brown body or boxy ceramic power type) may open up if there was a shorted switching transistor. Power resistors supplying current for the startup circuit may open from age.

These usually serve as fuses in addition to any other fuses that may be present (and in addition to their function as a resistor, though this isn't always needed). Since your FR has blown, you probably have shorted semiconductors that will need to be replaced as well. I would check all the transistors and diodes in the power supply with an ohmmeter. You may find that the main switch mode transistor has decided to turn into a blob of solder - dead short. Check everything out even if you find one bad part - many components can fail or cause other components to fail if you don't locate them all. Check resistors as well, even if they look ok.

Then, with a load on the output of the power supply (don't use the VCR itself just in case there is still some problem that could damage it) use a Variac to bring up the voltage slowly and observe what happens. At 50 VAC or less, the switcher should kick in and produce some output though correct regulation may not occur until 80 VAC or more. The outputs voltages may even be greater than speced with a small load before regulation kicks in. If you do not have a variac, put a 75 watt bulb in series with the line to limit current should there still be a problem. If the supply functions properly, the bulb should not interfere.

Picture jittering vertically may be similar problem. Tape is not moving smoothly over the head drum. (Daniel Schoo)

When you start getting an unusually noisy (snowy) picture, try the VCR with a different TV? It could be that the signal from the VCR is just a little weaker than it is used to be. Try moving the channel 3/4 switch back an forth - it may have developed a bad contact. Try the other channel (3 or 4) - it may work better.

Verify that the direct VIDEO OUT works fine. If this is noisy as well, then there are other problems.

A weak or defective RF Modulator can introduce snow. This would show up playing tapes as well as using the VCR's tuner. Exact replacements and generic versions are available from MCM Electronics or other electronics distributors for about $25 or less.

On a VCR which has been cleaned and with good rubber parts:

1. VCRs have a light or LED (IR, infrared) in the middle of the mechanical assembly that detects the end of tape. When a tape is loaded the tape will cover the sensor. The controller can tell if the tape is at the beginning, middle, or end by the sensor. The is achieved by a clear leader at the beginning and end of the tape. The microcontroller will detect a problem if the sensors do not detect the light or LED (middle of tape) and the carriage assembly is up (no tape loaded). The VCR will shut down.
2. If you have an incandescent light and it is not lit, it is burned out. If you have the LED type you can buy an LED tester from an electronic parts supplier or construct one as described at the end of this document. Replacement LEDs are readily available.
3. The VCR might be in a confused state. Many VCRs have a belt that drives a loading motor. This is the motor that drives the tape around the heads. If those guides are not fully retracted, the VCR shuts down.
4. Ensure the tape guide arm assembly is fully retracted by physically turning the gear assembly. Replace the belt.
5. Some obstruction is preventing part of the mechanism from resetting. Visually inspect for foreign objects or rough edges on something preventing full movement. Dried up grease can also cause this.
6. A gear has slipped a tooth and one part of the mechanism does not track another. This may happen if a tape was forcefully ejected after being eaten. You may find that a tooth has actually broken off.

• Determine if it in the video signal or is it only present when the VCR is close to or sitting on/under the TV?

• Does it happen when watching from the antenna/cable but a tape is playing or recording?

• Have you rearranged your setup recently? It is common for TVs and VCRs to interfere with each others operation.

• Did this just start suddenly?

• Is the quality of the video otherwise good?

• Does it matter what tape speed is used?

• Does it also occur during record?

If this is a >=4 head machine, SP and EP may use a different set of heads, so one or both SP heads may still be dirty or bad. If the machine tracks perfectly in EP, then alignment is probably fine - EP is more critical as to alignment as the EP track is 1/3 the width of the SP track.

Have the video heads been cleaned using the proper procedure (not just a cleaning tape - see section on video head cleaning).

New video heads may fix this, though it can be caused by other problems such as weak read electronics. See the section on video head problems.

You should also check the backtension adjustment - if too loose, head to tape contact will be compromised. Try increasing it momentarily by pushing the backtension lever slightly to the left while the tape is playing. The usual way to adjust backtension without a backtension meter and service manual is to look at the image just before vertical retrace at the bottom of the screen - this is normally not visible unless you can reduce vertical size or play with vertical hold to get the vertical blanking bar to appear. Of course, most modern TVs don't have any such controls! This is the head switching point and when the backtension is properly set the image above and the bit of image below this break will be approximately aligned.

If increasing backtension helps, either the heads are marginal or the backtension was low. However, low backtension will usually show up as a waving or flagging effect at the top of the picture.

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 end-of-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 and wind the tape around the drum.
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.

1. Everything occurs as above except that the takeup reel does not turn and tape spills into the machine. This is sensed by the microcontroller and it shuts down and unloads the tape. 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 you to order a new idler tire.
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'.
3. 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 would 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.

• I assume that you have cleaned it and replaced any dead rubber parts.
• I also assume that someone (we won't name anyone) has tweaked just about every mechanical adjustment.
• I would adjust the audio/control (A/C) head as best you can (don't touch this unless you know it was messed up by someone):
  • play a tape that you know was recorded on a good machine. It may be easier to start with a tape recorded in SP mode since this is less critical. Once the basic alignment is complete, go back and fine tune with a tape recorded in EP.
  • adjust the A/C tilt as vertical as you can by eye. If necessary, fine tune it for most stable tape movement - tape should be at same angle moving over takeup roller guide, A/C head, and adjacent fixed I guide.
  • adjust the A/C height for loudest sound. At each end of the range of this adjustment, you will lose tracking/sync and tape speed may fluctuate (in addition to the sound becoming weak).
  • adjust the A/C azimuth for best treble (high frequency) sound. This is a precise adjustment - a 1/16 of a turn is significant. There will be a very small range over which the sounds will be clear and natural. Music is best for making this adjustment.
  • with electronic tracking control centered, adjust A/C mechanical tracking (usually, a conical nut that moves the entire A/C assembly) until you get the least snow (if you have a picture at this point). Satisfactory tracking may be obtained at several positions of this control. However, only one will produce current video-audio sync. For the others, the words and the picture will be off by some multiple of 1/30th of second.
  • You may need to go back and touch up some of these again.

This doesn't require a scope - the video picture is an excellent alignment tool! It does take patience and a steady hand.

Also, have you touched any other mechanical adjustments - other guideposts, etc? Hope not. Also, I assume that any repairs to the guideposts have left them perfectly vertical - if they are tilted, then other tape path instabilities can result.

The following checks and adjustments are made in PLAY mode.

There is a ridge on the lower (stationary cylinder) on which the tape should ride - not above and not below. If it is not, first verify that the roller guides are snug against the V-stoppers - the brackets at the end of the tracks where the roller guides stop in PLAY and REC. If they are not, then you need to determine what is binding or what has fallen off of the tape loading mechanism. See the section on roller guide problems. Assuming that the roller guides are correctly positioned on the tracks, the first step is to visually adjust the roller guides so that the tape just rides on that ridge on the lower cylinder. That ridge is part of the guide mechanism.

There will be a set screw to lock each of the roller guideposts from turning. The appropriate one(s) will need to be loosened slightly - just enough to that the post is snug but can be turned by hand. Adjust each guidepost so that the tape just rides on top of the ridge.

Now, for the fine adjustments:

Left guide -> mostly problems with top of picture.
Right guide -> mostly problems with bottom of picture.

They can also cause a periodic loss of sync on a several second cycle.

Make careful ***small*** adjustments of each one - then wait for a few seconds for any results to become apparent. Since the tape moves so slowly, it takes several seconds for the tape motion to stabilize to the new guide position. The left guide will effect the top part of the picture (mostly) and the right guide will effect the bottom.

Once you are happy with SP, get a tape recorded on a known good deck in SLP (EP) mode since the tracks are narrower and fine tune it.

Tape path alignment comments:

1. An EP recording requires the best tracking, and will thus make the best test source. (But it must have been recorded on a unit that was aligned properly).
2. Using forward and reverse search modes helps to narrow the adjustment. The guide height on the "feed" side for whichever direction you're going will have more affect. In other words, tweak one while searching forward, and the other while searching in reverse.
3. You could have the tape centered at the middle of the contact path, but too low at one end and too high at the other.
4. You could have the entire contact path too high or too low, and be inadvertently "correcting" by misadjusting the tracking control. You could be off by an entire track getting a good but very unstable picture since the ridge is not providing any guidance.

1. Roller guides not fully engaged against 'V-stoppers' (the metal brackets at the end of the track on which the roller guide assemblies move when entering PLAY or RECORD modes. Common causes:
   • Obstruction or ridge on track preventing guides from completing their movement. Visually inspect and observe behavior while entering and leaving PLAY mode. Sometimes with use, an edge develops and the guide gets hung up. A fine file can sometimes remove this.
   • Parts have fallen off (don't laugh - JVCs tend to do this). Various parts of the mechanical linkage that move the roller guides may loosen with use and either fall off entirely or change position enough to prevent full engagement. Compare left and right roller guide assemblies, they are usually nearly identical in their operation and you should be able to identify parts missing or out of position. These are usually on the underside of the deck and will necessitate removing the bottom cover (unplug the unit!). To gain access to critical parts of the linkage which may be obscured by circuit boards or other components, you may need to power the VCR, turn it on, press PLAY, and then pull the plug just as the roller guides are in the middle of the track and accessible.
   • Tracks on which roller guide assemblies slide are dirty and/or need lubrication.
   • Obstructions such as toys or Cheerios blocking tracks.
   
   Check the roller guides while the machine is playing a tape. They should be firming pressed against the V-stoppers. Any looseness indicates a problem preventing full engagement. If pushing the offending guide into position fixes the tracking problem, this confirms the diagnosis.

   Note that in modes where the roller guides are retracted, the roller guide assemblies are relatively loose and free to move. However, the amount of movement possible should be similar for the left and right roller guides and you should not be able to lift either entirely off of the track - the ability to do so means missing parts underneath the deck. If the missing parts can be located, they can usually be glued back into position.

2. One of the fixed guide posts next to roller guides (the ones that are tilted about 20 degrees) have worked loose and fallen off. There should be a tilted guide post next to each roller guide. If one is missing, it has probably fallen into the machine. Immediately unplug (to avoid the possibility of it jamming something and/or shorting components in the electronics). Locate the escaped post - turn the unit upside down, sideways, shake it, whatever until the loose post falls to the table or floor. Glue it back into position with a drop of Epoxy or other household cement.
3. The backtension band has come loose or broken. The backtension band provides the force needed to keep the tape pressed against the video and audio head. A backtension lever on the left side just as the tape leaves the cassette is connected to a felt lined metal band that presses against the edge of supply reel. The position of the level determines the tension and is set up with mechanical feedback so that the tape tends to move it against spring force just enough to provide the correct amount. Test by moving the backtension lever a bit in each direction - you should be able to observe the tension change. Backtension bands are easily replaced. See section on backtension adjustment.
4. Mechanical damage due to trauma such as VCR falling off of TV. Cure, if possible, will depend in extent and type of damage.

Test the remote with an IR detector. An IR detector card can be purchased for about $6. Alternatively, build the circuit at the end of this document. If the remote is putting out an IR signal, then the remote or the TV or VCR may have forgotten its settings or the problem may be in the TV or VCR and not the hand unit.

Problems with remote hand units:

• Dead batteries - solution obvious.
• Corroded battery contacts. Wipe off chemical deposits. Clean with pencil erase and/or sandpaper or nailfile.

• Broken connections often between battery contacts and circuit board, possibly on the circuit board - resolder.
• Bad resonator or crystal - replace, but diagnosing this without an oscilloscope may be tough.
• Dirt/spills/gunk preventing keys from operating reliably. Disassemble and wash rubber membrane and circuit board with alcohol or soap and water - dry completely. Conductive rubber pads may have deteriorated or worn out, or contacts on circuit board may have worn or corroded. Various approaches may work including conductive Epoxy on circuit board pads, aluminum foil glued to rubber pads, etc.
• Cracked circuit board - can usually be repaired as these are usually single sided with big traces. Scrape off insulating coating and jumper breaks with fine wire and solder.
• Bad LED. If IR tester shows no output, remove LED and power it from a 9V battery in series with a 500 ohm resistor. If still no output using tester (these are nearly always invisible IR), replace with readily available high power IR LED.
• Bad IC - throw it away! This is usually quite unlikely.

The technology of video recording makes interesting reading and the sophistication of the circuitry and mechanism of a $200 VCR is quite amazing.

Component values are not critical. Purchase photodiode sensitive to near IR - 750-900 um or salvage from optocoupler or photosensor. Dead computer mice, not the furry kind, usually contain IR sensitive photodiodes. For convenience, use a 9V battery for power. Even a weak one will work fine. Construct so that LED does not illuminate the photodiode!

	+9V ___/ ___
		    |---------+
	 	    |         |
	 	    \         \
	 	    / 3.3K    /  500
	 	    \         \
	 	    /         /
	 	    |       __|__
	 	  __|__     _\_/_  Visible LED
	IR ---->  _/_\_       |
	      PD    |     B |/ C
	 	    +-------|  2N3904
	 	    |       |\ E
	 	    \         |
	 	    / 10K    _|_
	 	    \         -
	 	    /
	 	   _|_
	 	    -