question about demagnetizing audio head on VCR to improve audio

[jimdagys]

I am in China and just got a used VCR because the previous one broke. In China, unlike in USA, new VCRs have not been sold retail for over 20 years, so only used ones are available, and are quite rare. The problem is, on this VCR that I just got, the audio volume is down a bit, and a little distorted. This problem occurs on prerecorded or just recorded material. The problem is not the tape because the audio was fine on the previous VCR. This VCR (not stereo or hi-fi) uses a simple audio head that is next to the control track head. My question is, do you think that demagnetizing the head will improve the sound? Does this kind of problem often occur with VCRs?

[MysticE]

I assume you have thoroughly cleaned all the recording/playback heads with alcohol.

[wtsinnc]

You could try it, but every VCR I've ever owned had an automatic demagnetizing circuit for the audio head which would do it's thing when the unit was powered off. Symptoms of a magnetized head include muffled sound/loss of clarity, decreased volume, and in severe cases, a popping or crackling noise. If the head is severely magnetized, it can actually act as an erase head, partially or totally damaging the audio track.

If you have cleaned the head as well as everything else that the tape comes in contact with and the problem still exists, you could very well be dealing with a magnetized head, but the problem could also be caused by improper alignment or severe wear. Inspect the audio head and look for a smooth, clean surface. Whatever wear has occurred should be evenly distributed and the head should be free of horizontal grooves cut into the face. If you see these grooves, odds are good that the head is damaged- probably beyond repair. Finally, look at the record gap in the erase head; it should be very thin but well-defined and the areas to the left and right of the gap should be smooth and free of any appearance of abrasion.

If you do decide to use a demagnetizer, be careful not to physically touch the head with it. The proper procedure would be to turn the demagnetizer on at least three feet away from the head and slowly move it toward the head using a tight circular pattern. Hold the circular pattern at the head for 2 to 3 seconds, then slowly move the demagnetizer away from the head maintaining the circular pattern. Once the demagnetizer is again about three feet away from the head, turn it away from the VCR and turn it off. During this process, leave the VCR powered on.

[wtsinnc]

Addenda to my earlier post:

Error. I wrote that the VCR should be turned on during the demagnetizing process.
-WRONG-
The VCR should be turned OFF.

My apologies for the error.