Got two similiar late 80's JVCs, both are 4-head mono and basically have
the exact same problem. The bottom half or so of the picture is just snow,
the top is normal but it looks like the bottom of the picture pushed up to
the top of the screen. Now here's the interesting thing: every time the VCR
is powered, the amount of snow changes. Next time, there might be 75% of a
picture, or 25%. It seems to be completely random. Tracking adjustment makes
no differnence, and the tape path is aligned properly.
Tried swapping out the power supply and head preamp boards, but this made
no difference. Perhaps the replacements were bad too?
Anything else I could check, without a service manual? These are both
really nice machines (one is a commercial unit in a white case) and I hate
to just junk 'em.
Thanks for any advice.