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Notes on VCR Troubleshooting and Repair INDEX V.
Chapter 14) SIGNAL AND INTERFERENCE PROBLEMS

14.1) VCR color problems

There are two typical situations:
Playback is always in B/W.
Record is B/W but playback has normal color.
If you can play prerecorded tapes in color but tapes recorded on this VCR do not play back in color, there may be several possible causes. The simplest is that your input signal is too weak - a misadjusted antenna or cable with a large number of splitters - and the VCR's color killer thinks there is no color. Sometimes the threshold for detecting the color signal is set higher on the VCR than the TV which you are using to monitor the recording.
Some questions:
Is the color TV's fine tuning set correctly?
Does it play prerecorded tapes in color?
Does the tuner output produce color?
Does the video output work in color?
Is the problem the same for all recording speeds?
Do the tapes you record on this VCR play in color on another one?
If the answer to all but the last question is 'yes', then the problem is most likely in the video/chroma circuitry associated with recording function. It could be as simple as the color killer setting being too low.
Possible sources of problems with color recording:
Weak signal - check and/or adjust antenna.
Color Killer set to low.
Problems in tuner - does the video output work in color from the tuner?
Problems in chroma circuits.
Sometimes, marginal heads - less likely if it plays in color.
If recording works fine as indicated by tapes made on this VCR playing fine on another one but prerecorded tapes do not play back in color and the VCR works fine in all other respects there could be several possible causes:
Weak chroma signal level from VCR.
Color Killer set to low on TV.
Problems in chroma circuits.
Marginal or dirty video heads.
Note that in all cases of missing color, checking with another TV and/or adjusting the TV's controls should be tried first as slight differences in signal levels between tuner and playback may cause a TV with marginal settings (fine tuning, color killer, chroma circuits) to switch unexpectedly between color and B/W.

14.2) RF signal problems

First determine whether there is a problem with broadcast or cable, playing tapes, or both. If it is only broadcast or cable, then your source may be at fault. If it is fine with the VCR off but noisy when using its tuner, the problem could be in the tuner itself.
Verify that the direct video output (RCA jacks) works properly with a prerecorded tape. If this is noisy as well, then there are problems with the video circuitry or video heads.
If there are problems with the Channel 3/4 output but the direct video outputs are fine, then suspect a weak or dead RF modulator. This is a little metal metal box with the Antenna In and TV Out connectors. It has circuitry which switches between the VCR's internal video signal and the antenna input. It also converts the video baseband signal to the channel 3/4 output required by the TV.
Before you conclude that the RF modulator is to blame, check that the channel and fine tuning of the TV are properly set and that there are no other problems with the TV. Test the VCR with another TV. It could be that the signal from the VCR is just a little weaker than it is used to be. Try moving the channel 3/4 switch back an forth - it may have developed a bad contact. Try the other channel (3 or 4) - it may work better. Try moving the VCR away from the TV - sometimes interference from the TV will degrade the video quality.
If you do conclude that the RF modulator is at fault, generic replacements are available from the parts sources listed near the end of this document or other electronics distributors for less than $25. Replacement is straightforward since there are only a couple of soldered connections but getting to the unit physically is sometimes a challenge.

14.3) VCR will not tune broadcast or cable

Are you sure that the input signal is making to the VCR? Does the passthrough connection work? Double check the connections. Connect the cable you have on the ANTENNA IN of the VCR directly to the TV. Make sure it's center pin is not bent over or broken off. Try a new cable. Is the tuning mode switch (broadcast, CATV, etc.) set correctly on the VCR?
If the signal is preset into the VCR, there still may be a bad connection inside preventing it from making it to the VCR's tuner. Sometimes, there are RCA style plugs inside that work loose.
Otherwise, the tuner of the VCR is not working. This could be because it is broken or power to it is bad or missing. If all other functions of the VCR are working, it is likely (though not guaranteed) that the power supply is fine. There could be bad connections or dirty connectors as well. Beyond probing for bad connections and verifying your antenna hookup, there is not much that can be done without a service manual and test equipment.

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 other's 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?
Some model VCRs just do not want to be close to other equipment like TVs. Your only easy fix may be to shuffle the components in your entertainment center.

14.4) Firing (static) lines in picture during playback

These may be described as static or short bright or dark lines in the picture. They usually have a sharp start and may trail off or stop abruptly. They may be occasional (once every few seconds) or frequent (multiple instances per video frame). Also see the sections on video head problems as large quantities of firing lines may be due to dirty, worn, or defective video heads. First, try a different tape - preferably a new recording made on a different VCR or a new commercial video. It is possible that these streaks are simply due to dropouts on the tape - missing bits of oxide or dirt causing momentary loss of video signal. Old, worn, or cheap off-brand tapes are particularly prone to dropouts.
One characteristic of dropouts is that they may span video lines as well as video frames. If your lines are very short and random, they may be caused by a dirty, missing, or improperly positioned video drum static brush. In most VCRs, you will see a metal strip with a carbon contact pressing against the center of the video drum spindle either above or below the deck. It is there to provide electrical contact between the rotating video drum and the stationary lower cylinder and chassis. This is necessary since the bearings on which the upper cylinder rotate may not provide adequate contact and any static buildup caused by the spinning head cylinder rubbing against the tape may discharge through the bearings resulting in these firing lines. Carefully remove the static brush and clean the end of the spindle and carbon contact. This may be all you need to do to remove the static lines from your picture.


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