You may think you are on the set of the latest sci-fi movie. The VCR displays are counting at random, pushing buttons produce unexpected results, motors may be spinning, or the VCR may be repeatedly loading and unloading a non-existent tape. I may be attempting to play a tape even without you pressing any buttons. While these could be symptoms of a actual problem, first try unplugging the VCR from the wall outlet (don't just turn it off) for a minute or so. If this does not help, try unplugging for a couple of hours - this will usually drain the backup battery and reset many other functions of the VCR. If one of these techniques results in the universe returning to normal, there may have been a power surge or lightning strike nearby which threw the microcontroller into a confused state. It may never happen again. However, power surges can be the result of heavy appliances like air conditioners on the same circuit. If this is the case, you should consider using a different circuit for your electronic equipment. If this behavior started when the VCR was just plugged in or following some other action requiring the mechanism to move or initialize, check for mechanical problems like a broken belt or one that has popped off its pulleys or an obstruction like a rock or toy that is preventing the VCR from completing the required motions. Also see the section: "VCR is failing the power-up sequence". Once you have ruled out mechanical problems, it is likely that the VCR has a microcontroller, power supply, or other electronic problem which may require professional service.
Normally, the AC line provides power to retain the clock, active channels, and programming settings. During a power failure, the clock and programming is usually powered using a supercap or battery (usually rechargeable). Channel settings for older style varactor type tuners were often stored in some kind of non-volatile memory while active channels for quartz tuners generally use battery backup. The clock and programming backup may be a supercap - a very high value special electrolytic capacitor - as much a 1 F (1,000,000 uF) at 5-12 V. Alternatively, it may use a rechargeable NiCd battery. In either case, these are easily replaceable with standard parts. A NiCd battery pack of similar ratings should be readily available. Supercaps are available from large electronics distributors. NiCd batteries fail in two ways - loss of capacity or shorted cells. If memory is retained for a much shorter time than it used to, then the battery has probably lost most of its capacity. If you measure less than n x 1.2 V for an n cell NiCd battery pack after it has been charging for awhile, there is likely a shorted cell. In either case, the best solution is a replacement though the various common techniques for rejuvenating NiCd battery packs can be attempted (remove from VCR first!). The non-volatile memory could use a special chip like EEPROM which does not require power or a battery backed SRAM or be internal to one of the VCR's microcontrollers. Channel memory may use a separate power source from the clock and programming, possibly a Lithium battery since it is undesirable for the channel settings to be forgotten even if the VCR is unplugged for a month or more as it is such a pain to reinitialize them. Rechargeable batteries have too high a self discharge rate.
This usually means that one or more of the voltages to the vacuum fluorescent display (VFD) are missing or that the display controller is bad. If the front panel suffered physical damage, the display tube, circuit board, or other components could be damaged. The VFD requires around +30 VDC for the tube anode and 4 to 6 VAC or DC for the filament. Its cathodes in the form of character segments or formed words or symbols will likely be driven directly from one of the controller chips. Remove the front panel and with the VCR plugged in, turn out the lights and inspect the filament, several very fine wires running the length of the display. They should be glowing a very faint red-orange. If you see nothing, the filament voltage is likely missing. Filament voltage may come directly from the power transformer (if a non-switching type power supply) or be one of the DC outputs of the supply. Check around the VFD for the +30 VDC (approximately). If this is missing, there will be nothing displayed. In some VCRs like those manufactured by Hitachi, a separate DC-DC converter module provides power for the display only. See the section: "Dead clock in Hitachi manufactured VCR". Look for bad connections, open resistors, blown IC protectors or fuses, etc. Of course, if the VCR has an on-screen display, you will be no worse off than many newer models that have done away with the front panel VFD entirely! (From: Paul Grohe (email@example.com)). The fluorescent display in most VCR's require three voltages: 1. The filament requires a floating 3 VAC. 2. The filament has to be biased at -12 V to -15 V 3. The segments need -20 V to -30 V to light. The DC-DC converter usually provides a "floating" 3 VAC winding, a low current -12 VDC tap connected to one of the filament leads, and a -20 VDC to -30 VDC segment drive voltage. If you look really, really closely at the display, you will see the faintly glowing filaments stretching across the length of the display.
First, don't ignore the possibility that you are attempting to play an old, worn, or defective tape. This is especially true of rental tapes which have been through who knows what kind of VCR hell. The control and audio tracks - along the edges of the tape - are the first to wear. Weak muddy sound and erratic tracking are also common symptoms caused by old worn tapes. There have even been instances of new name brand tapes which were cut too wide - though this would be extremely rare. To confirm that it is your VCR doing the dastardly deed, play or record for at least a minute on a tape known to be in good condition. The use REV to back of the tape for about 15 seconds. Eject and open the cassette door by releasing the latch and inspect for edge crinkling. Any rippling along either edge of the tape is an symptom of a possible problem. It isn't only that the tape does not make good contact with the audio or control head (depending on which edge is damaged) but just an indication that the tape may not be moving through the transport precisely positioned. Assuming you are having the same problem on multiple tapes and that using a known good (new) tape results in damage: This is an indication that your tape path alignment is off or your rubber parts (probably the pinch roller) need replacing. The tape is wandering up and down as a result of unequal pull from the capstan due to a glazed/worn pinch roller. There could also be other aspects of tape path alignment like roller guide tilt (which is probably not adjustable), A/C head tilt, dirt, roller guide height (don't mess with it), etc. See the chapter: "Tape Path Alignment and Backtension Adjustment. It could also be worn feet on the roller guide assemblies causing the guides to not be perfectly vertical. Replacement of these parts may be the only cure. Other much less likely possibilities: excessive or varying backtension, tight idler clutch, electronic problems. For a VCR with very high mileage, it is also possible that there has been a ridge worn in the surface of the control head preventing consistent contact between it and the tape: (From: Phil Reed (firstname.lastname@example.org)). "One thing that can happen is that the control track head gets a ridge on it (due to wear) which prevents the tape making good contact with it. This can make the tracking go mad and sometimes even mute the video. Pausing the VCR overrides any muting, resulting in a clean still picture. Another clue is that some tapes will do it worse than others, this is due to slight variations in tape width or condition." Other related symptoms include: * Sound does not always appear at full volume or normal quality for a few seconds after the VCR starts playing. It may vary in loudness during play as well. Slightly changing backtension may make a big difference in audio. * If your VCR has autotracking, its indicator may be flickering as the logic attempts to solve an impossible problem. * On HiFi VCRs, there will likely be no HiFi sound as its tracking is even more critical than video tracking. * Tape speed may be changing resulting in wavering sound or even running (usually) faster than normal. This may be due to the control head not reliably reading the control track. If you look carefully, you should be able to see the tape wandering slightly producing the muddy sound and erratic tracking. The tape may not be perfectly smooth in passing over the various guides and rollers. Normally, you will almost not be able to tell the tape is moving at all except by examining the reel rotation - it is that mirror smooth. First, clean the tape path properly, especially the capstan and pinch roller, tape guides, A/C head. Inspect the pinch roller for glazing, cracking, etc. and replace if necessary. See the sections: "General guide to VCR cleaning and rubber parts replacement" and if necessary, the chapter: "Tape Path Alignment and Backtension Adjustment". Another possibility is that the control portion of the A/C head stack is dirty or defective or there are problems in the wiring or its circuitry. Double check that the tape is in solid contact with the bottom of the A/C head stack (where the control track is located), that the head is clean, its connector is clean and seated properly, and look for any broken wires or bad connections.
Normally, speed is controlled via phase locking the capstan to the 30 Hz control pulses read off of the tape via the stationary audio/control head. On a VCR with autotracking, the autotracking light may be flickering as well. Possible causes for loss of lock: * Dirt or bits of tape or oxide on control head - clean and inspect. * Defective control head. Try making a recording. If recording plays normally on another VCR, then control head is probably ok. * Tape wandering up and down so that control track is not sensed properly (how is the sound - this would also cause fluctuating or missing sound.) See the section "VCR randomly switches speeds, tracking problems, and muddy sound". * Mechanical fault preventing firm tape-control head contact such as a stuck movable guide post. * Mechanical or mode switch problem preventing firm capstan-pinch roller contact. Under certain conditions - possibly at the beginning of a tape when takeup tension is greatest - the takeup reel may have enough torque to pull the tape past the video heads without the capstan controlling the speed as it should. * Defect in servo or control circuitry or power supply (voltage out of tolerance). * Bad tape. Don't overlook this possibility especially if it is a old or rental tape. The control track may have gotten erased or warn off - it is at the edge of the tape. Try another tape. Inspect the tape path really really carefully to determine if there is some obstruction preventing tape-control head contact or other mechanical problems. Try cleaning the tape path and checking the rubber parts. Check power supply voltages if you can determine what they should be (see the section: "VCR power supplies". If these procedures to not reveal anything amiss, you will need a service manual to pursue electronic faults.
As always, rule out the possibility that this is just a bad tape. There have even been instances of new name brand tapes which were cut too wide - though this would be extremely rare. It could have been creased by someone else's VCR. Try a tape you can afford to sacrifice (though it will still be safely usable) and run it through the VCR. Sometimes, there will be a problem only near one end so you will need to try it at various sections of tape. Record a few minutes and then back it up a bit and inspect for damage by opening the cassette door (press the release on the side). Both edges should be perfectly flat and smooth. If you get similar playback symptoms with this cassette and/or find that the tape is being creased along one or both edges, then it is your VCR doing the dirty work. When the bottom of the tape gets creased, the control head may no longer align with the control track and you loose servo lock on the sync signal. Your audio may be fluctuating in intensity as well since the audio track is wandering also and the tape may be intermittently going in and out of correct tracking and/or changing speeds. Since the tape can no longer seat stably on the lower drum guide ridge, there could be other problems such as noise bars along the top or bottom of the picture, jumping, etc. It could be the guide posts or other tape path components, but before you turn every screw you can find and make the problems hopelessly worse, replace all of the rubber parts - belts, idler tire, pinch roller. And while you are at it, give the machine a good cleaning. A dirty, worn, hard, dried out pinch roller in particular can result in the tape wandering up and down causing tracking problems and creasing the tape in the process. This is probably the most common cause of tape damage assuming the VCR itself has not been abused (i.e., jammed cassette removed using a pair of Vice-Grips(tm)). With a thorough cleaning of everything before buying the new rubber (which BTW should not be more than a total $10-$15 from a place like MCM Electronics), you may at least see a temporary improvement in performance - and confirmation of the diagnosis. You really need to determine exactly where the tape is being creased. Once you do this, you may be able to determine the cause and visually verify whether the problem is affected by any of your adjustments or probing. Some other possibilities include: * Worn feet on the roller guides causing them to not be precisely vertical. Sometimes there are adjustments for tilt; usually there are none. Sometimes replacements are readily available (especially if this is a common problem with your model). * Cassette not seating properly. Press down on cassette while playing a known good tape. If it moves, then check for obstructions or foreign objects such as toys or peanut butter and jelly sandwiches! A dirty, oily, or just tired belt may not grip well enough for the mechanism to complete the cassette load cycle. * Oil seal washer on bottom of capstan has worked its way up out of place. Carefully push it back down and then clean the capstan shaft. * Various guides too high or too low but this is pretty unlikely unless they have loosened somehow. Don't adjust unless you have a service manual or are absolutely sure that they have changed height. * Backtension misadjusted (usually too great). If the tape passes around the backtension lever at too straight an angle (it doesn't bend enough), in addition to the possible incorrect (excessive) backtension, it may simply not seat properly when passing around the subsequent guidepost or impedance roller (that white plastic wheel that doesn't seem to serve any purpose).
Symptoms may be that the tape counter stops moving and/or the VCR enters stop mode and shuts down. Assuming this is not a mechanical problem - bad idler, belt, etc., make sure you don't accidentally have an 'insert editing' mode enabled. Insert editing uses the previously laid down control track as the timing reference. This provides clean glitch-free transitions between scenes. Insert editing will not work at all on a new or bulk erased tape. If you routinely use your cassettes over and over, there will be varying amounts of previously recorded material - with control tracks - on the tapes. At some point your recording may start to use tape beyond the recorded sections and - presto, no more control track. Poor VCR is confused and aborts.
Make sure you are using the proper record button. Most VCRs have a OTR (One Time Record) or 'quick record' feature which starts just like normal record stops after a multiple of (usually) 15 minutes depending on how many times you press the button. The (normally) red button should be used for unrestricted untimed recordings. Some VCRs also have other timed modes - sort of like the timed off function of a clock radio. Pressing the 'Off-T' button adds time to record or play in 15 minute increments and then the VCR shuts off.
The result may be inconsistent positioning of the tape if you use the counts to locate programs. It might also result in the VCR aborting PLAY, REC, FF, REW, or search modes if it thinks that the counter is not changing as expected - missing pulses or skipped counts. For real-time counters, this may mean a problem deep in the electronics requiring a service manual. However, if you are attempting to play a tape that has nothing on it, the real-time counter will not change. This is normal as there are no control pulses on the tape. For non-real-time counters, if the display skips counts or 'free runs' - counts very quickly at certain times, this could be due to a defective sensor or hysteresis circuit. If it counts in the wrong direction, a logic problem is indicated as direction is determined by the microcontroller being aware of what mode the VCR is in - there is likely no actual direction sensing on the reel. See the section: "Reel rotation sensor testing" for further information.
If the VCR works in all respects when tuning broadcast or cable channels but playing a tape results in no picture, a very snowy picture, or just a blue screen, there may be problems with the video heads, the lower cylinder, head preamps, or other video electronics. Testing most of these is beyond the scope of this document and will require a service manual and test equipment. However, you can do a decent job of determining if the video heads are likely to be at fault. Sometimes, when snow or serious video noise suddenly occurs while playing a rental, old, or damaged tape, it means the video heads have picked up some oxide and are no longer making good contact with the tape. Letting the VCR play a newer tape for a few minutes may clear this if it is minor. However, video head cleaning (using a cleaning tape or the manual procedure described in the section: "Video head cleaning technique") will probably be needed. But, first start with the section: "Snow on one or more speeds" and NEVER NEVER attempt to clean the video heads without using one of the recommended techniques - you can easily destroy the heart of your VCR! Also, never attempt to play or record on a spliced or seriously damaged tape as this can also result in destruction of the video heads.
If attempting to record results in unexpected behavior, there could be a variety of causes depending on what you get for playback: * Attempts to record are ignored by the VCR or cause the cassette to be ejected. This may mean that the record protect tab on the cassette is broken off or the record tab sense switch is dirty or bad. * Record (either manual or timer) stops at random times - possibly with flashing display and/or ejects cassette. This could be the result of a dirty or defective record sense switch or misalignment preventing proper engagement with it. Some VCRs check for the record tab constantly while others just check when the REC button is pressed or the timer initiates record. It could also be a defective reel or tape end sensor halting record though these would likely affect playback as well. * Playback results in video snow and whatever was on the tape, if anything, is gone. This means that the old recording is being erased (if there was one) but nothing or too weak a signal is being written by the video heads. This could be due to a variety of electronic faults as well as marginal or bad video heads. * Playback results in a picture but it has a wiggling rainbow pattern running through it. This is normal at the start of a recording made on top of an old recording if your VCR does not have a flying erase head. However, it should wipe down the screen in a few seconds and disappear. If it does not go away, then your full width erase head is not working. * Playback results in a flickering picture alternating between good video and snow at the frame rate (about 30 Hz for NTSC). This could mean that one of the two heads used for record is dirty or defective. * Playback results in proper video but the previously recorded or no audio. The audio dub switch (if any) may be in the wrong position or the audio circuitry may be defective. * Playback results in a picture which is cycling in brightness or flashing. This likely means that you are attempting to record (copy) a Macrovision(tm) (see the info at: http://www.repairfaq.org/filipg/LINK/F_MacroVision.html) or some other copy-protected tape or your cable or satellite company is transmitting copy-protected video. Some of the new digital DBS satellite receivers output a Macrovision copy protected TV signal so you can't tape the movies from them either. Newer VCRs will generally not record successfully. Some older VCRs will record without problems. See the section: "Why VCRs will not copy (Macrovision) copy protected tapes". (8mm VCRs may record the entire signal and therefore be able to playback successfully. However, attempting to copy the 8mm tape onto a VHS tape will result in the same problem.)
Did the problem happen suddenly? Or develop over time? If suddenly, what were you watching at the time? A (literally) dirty rental movie? If this VCR has 4 or more heads, SP and EP may use a different set of heads, so certain heads may still be dirty or bad. If the machine tracks perfectly in EP, then alignment is probably fine - EP is more critical as to alignment as the EP track is 1/3 the width of the SP track. Have the video heads been cleaned using the proper procedure (not just a cleaning tape - see the section: "Video head cleaning technique"). New video heads may fix this, though it can be caused by other problems such as weak read electronics. See the chapter: "Video Heads and Upper Cylinders". You should also check the backtension adjustment - if too loose, head to tape contact will be compromised. Try increasing it momentarily by pushing the backtension lever slightly to the left while the tape is playing. The usual way to adjust backtension without a backtension meter and service manual is to look at the image just before vertical retrace at the bottom of the screen - this is normally not visible unless you can reduce vertical size or play with vertical hold to get the vertical blanking bar to appear. Of course, most modern TVs don't have any such controls! This is the head switching point and when the backtension is properly set the image above and the bit of image below this break will be approximately aligned. If increasing backtension helps, either the heads are marginal or the back- tension was low. However, low backtension will usually show up as a waving or flagging effect at the top of the picture.
This means that there is one or more horizontal lines during playback that are at fixed locations on the screen. These could be the result of electronic problems or marginal video heads but the possibility that should be explored first is that of tape damage. If a prerecorded tape that plays properly on another VCR, shows the effect on the suspect VCR - AND - then shows the same thing on the other VCR, it is being damaged by something in the tape path. Open the door of the cassette by releasing the catch on the side. Look carefully at the surface of the tape - it should be mirror smooth all across. If you see any evidence of hair fine (or larger) scratches running the length of the tape these are what are causing the line. This is likely a result of a bit of debris or a rough edge on one of the guide posts in the VCR. Get a brand new tape or a known good tape (that you can afford to mess up) and test it on another VCR (at the tape speed that is worst, if this matters). Assuming playback is fine, play it on the suspect VCR for a couple of minutes. Pull the plug (DON'T hit STOP) so the transport remains in the fully loaded position. Now, carefully examine the surface of the tape all along the tape path (disturbing its position as little as possible) to identify the location where the damage begins. It may just be a bit of something stuck to a guide post. Has the VCR been cleaned in the last 10 years? Note: This sort of damage to the tape does not represent a risk to your VCR's video heads so you can continue to use the tape if desired.
You have a VCR with known good heads that produces jumpy (vertically) video in play that cannot be stabilized with the tracking control. Perhaps you have attempted to adjust the mechanical tracking and maybe some other stuff. Some questions: * Did you replace the heads? Could you have gotten them 180 degree rotated from the correct position? I don't know what the implications would be on your model VCR, but there is a definite right and wrong on this. It would certainly show up as tracking being way out when attempting to play back tapes recorded on this VCR on another machine. * Exactly what adjustments did you touch? * Have you verified that the roller guides are fully engaged against the stops? * Have you checked backtension? * Did you touch roller guide height? This is probably a mechanical problem, most likely an adjustment or fault related to tape path alignment. However, it could also be due to electronic problems with the video or servo circuitry. The vertical sync could be corrupted or the head switching point not set correctly. The head switching point is 6.5 lines before vertical sync. If this ends up moving into vertical sync for some reason, you will get unstable video. The supply side roller guide height adjustment is also critical and would be the first thing to check mechanical alignment problems are suspected. However, don't overlook the obvious: your TV is marginal or misadjusted or you are attempting to play a bad tape.
Note that on a 2 head VCR, it is not possible to display a noise-free picture on a tape recorded at the SP or LP speeds. Therefore, for rental or pre-recorded tapes, what you are seeing may be normal. A 2 head machine should execute these special effects perfectly fine with EP(SLP) recorded tapes, however. VCRs with 4 or more heads will usually have a V-Lock adjustment - either a knob on the front or rear panel, or sometimes 'conveniently' accessible from under the VCR. Sometimes, a special tool is needed to adjust this control. Where tracking is adjusted with a set of +/- buttons, these may also be used in PAUSE mode. There may be separate adjustments for SP and EP(SLP) speeds as well. In any case, these settings are made while viewing a tape recorded at the appropriate speed in PAUSE mode. For LP speed - which is being phased out by many manufacturers, at least for record - these special effects usually do not work well if at all. This is basically due to the nature of the sync signal alignment on tapes recorded at LP speed and would require complex circuitry to handle properly at anything other than normal LP play speed. (If you care, the sync tips between adjacent tracks align on the tape in SP and EP recorded tapes but are off by 1/2 line with LP recorded tapes. This results in the tearing seen in search modes with LP recorded tapes.) Since this tape speed is of little true value - it is a compromise anyhow - the added expense has been found not to be justified except on professional machines.
This may be a 'feature' of your VCR. On some older models, the designers in their infinite wisdom (or that of their marketing departments) decided that no picture or no search capability at all was preferable to a picture with serious noise bars or one which didn't sync properly. This was usually before the days of 4 head VCRs which directly addressed at least some of these issues. Most 2 head VCRs will work fairly well on EP recordings but show noise bars over about 50 percent of the picture with SP recordings. For those made at LP speed, tearing will occur in addition to noise bars if they sync at all. Few VCRs deal properly with LP search as substantial additional circuitry is required. In my opinion (IMO), any picture is better than a blank screen or no search capability.
Problems will be similar to the following: "I have a General Electric VCR model VG4217 that's displaying the most unusual problems. When I play back a pre-recorded tape from a video store it plays fine. When I play back a tape recorded on the machine I get video noise for 4 seconds then clear pix, then video noise for 4 seconds, then clear pix and so on. I also noticed that if I have the tape counter displayed on the screen, and when the counter progresses its count, the tape plays properly. Then all of a sudden the counter stops counting and the problem continues again. I have cleaned heads well, cleaned tape path, and even cleaned the underside of the takeup reel, all to no avail?" First, make sure the tapes are in good condition. They may have been damaged (edge crinkled) before you serviced the VCR. This is now causing your erratic behavior and there is nothing wrong with the VCR. Before considering drastic action, record on a brand new tape - from end-to-end if the initial results seem promising. You may have a non-problem. Try recording you your VCR and playing back on another one. If this works, then bad tapes are the most likely explanation. If this does not work, there could be electronic problems: (From: Stephen Isaacs (email@example.com)). The normal playback of a pre-recorded tape suggests most things are working fine. The self recorded problems point to a faulty control track recording system. bad oscillator, or amp. It is also possible the erase head is not doing its job making it difficult to record a new control track over an old one. (From: Richard (firstname.lastname@example.org)). Almost all pre-recorded tapes are recorded at the SP speed. If you are like most people, you probably do your recordings at the EP speed (to get as much on the tape as possible). Do you have the same problem if you record at SP? Your VCR probably uses different heads for SP and EP. You may have dirty EP heads, defective EP heads, a head amp problem. Or, there could be a tape tension or other mechanical problem. (From: Frank D. Ralston (email@example.com)). Check the following: * Dirty (or worn) heads * Low back tension (common problem) * Tape path alignment (particularly input tape guide)
Symptoms like a picture which has a portion that is noisy or missing, or where the picture is split between top and bottom with the vertical blanking somewhere in between may indicate a problem with the PG sensor. The rotational position reference for the video head drum is usually supplied by a pickup in close proximity to the edge of the lower cylinder (probably) which has a small magnet fastened to it. This generates the so called 'PG' pulse and is used by the servo circuitry to properly control the drum rotation and the head switching point. If this sensor is moved or if there is a fault in the PG circuitry, a variety of record or playback problems can result. Without this reference, the servo circuitry has no way of knowing where the A and B heads are at any given time. During record, this may result in recording video which is not properly lined up with the video tape - a track may consist of the end of one field and the beginning of the next rather than an entire fields as it should. During playback, the head switching point may occur at the wrong time resulting in a partially snowy or missing picture since a head that is not even in contact with the tape may be active. Similar problems may make look like your TV's vertical hold control is set incorrectly with the vertical blanking bar visible at an arbitrary point on the screen. The assembly on which the rotating magnet(s) are mounted and the upper cylinder may be secured with one or two set screws. If these loosen, the the precise relationship may be lost resulting in a shifted head switching point. It may even be random - changing location each time the drum starts up due to the inertia of the upper cylinder. If this is the case, you will need a service manual to properly adjust the angular location of the magnet assembly unless there are obvious 'timing' marks to guide you. Beyond confirming that the pickup coil is in close proximity to the drum, the rotating magnet and sensor are secure, and that there are no bad connections or loose connectors, there is not much to be done for these problems without a service manual. The definitions below are just For Your Information (FYI): PG - pulse generator. The pulse is derived from the rotation of a magnet on the video head drum past a sensing coil. I suppose this could be done optically as well. FG - frequency generator. This is a signal (sine or square) derived from the rotation of the video head drum. This may be phase locked to the PG pulse but can be a multiple of the frame rate. This could also refer to the capstan or reel rotation rather than the head drum.Go to [Next] segment
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