Electrolytic capacitors have probably dried out and went bad in the capstan
or drum servo control circuits. When they go bad the servos can't compensate
for tape speed variations resulting in sound wow and flutter and snow lines
moving up and down the screen every few seconds. Usually the picture will be
fairly clear in fast forward and rewind modes since servo lock isn't needed,
but poor in regular play mode. The tracking control also becomes dead and
useless since the servos are way too far out of spec to compensate for.
Early 80s Sony Betamax units were notorious for this problem and Sony
capacitor repair kits were popular up until just a few years ago. You can
get a schematic and try to find out what electrolytics exist in the servo
control circuits and replace them. You can also try adjusting various pots
in those circuits to see if it will come back into spec as is, but you'll
still have big problems trying to watch tapes recorded from other machines.

You can buy totally reconditioned Beta machines by professional techs via
Ebay, but sometimes going for $200+ they're not cheap. The Sanyo 3900 was
far from a high quality machine.

"Comcast News" wrote in message
...

Any suggestions as to diagnosis, or leads on parts would be appreciated.
The model number is VCR-3900II.