Just replace that cap - the guys who suggested it are correct without any
doubt.

The switch point is checked by using a dual-trace 'scope and comparing the
SW30 signal to the video signal found at the VIDEO OUT jack. Trigger on the
SW30, and adjust the sweep to show the relative position of the leading edge
vs. vertical sync. Spec is 6.5 lines prior to vertical sync, + or - 1.5
lines.

Mark Z.

--
Please reply only to Group. I regret this is necessary. Viruses and spam
have rendered my regular e-mail address useless.


"Chris F." wrote in message
...
How do I check the switch point?

"Asimov" wrote in message
...
"Chris F." bravely wrote to "All" (13 Dec 03 00:11:47)
--- on the heady topic of "Old JVC VCRs - half of picture missing"

Tracking has no effect indicates that the transport servo is locking
randomly on noise and not on the proper head drum pulse. The cause is a
loss in value of the motor signal electrolytic cap on the head drum pcb
under the chassis. Check the electros for high esr or low capacitance.
After this is fixed make sure the switch point is correct. It is a
very common JVC problem.

CF From: "Chris F."

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