Have an SR-V10U currently not in use. It will play but video cuts out after a second or two, audio continues to play fine. video works in FF or REW as well as all modes of slow motion/frame by frame. I have gotten it to play a tape through once or twice. Counter works on and off, some modes sometimes other modes other times. From research and observing it loading and playing tapes, it appears the bearings on the capstan pinch roller are shot causing it to wobble more than usual which is raising and lowering the tape on the a/c head depending on what speed and direction the tape is traveling.
I spent many a night trying to figure this out, but I was driving my wife crazy with my obsession and I didn't want to buy a new pinch roller assembly arm from JVC (For way too much money) only to find out it was something else entirely. She (my wife) finally convinced me to go with a new unit and I just purchased an HR-S9600U on ebay
to replace it.
Long story short, I am not sure if it is what you're looking for, but I would be willing to part with it for relatively cheap even though it seems like its a small repair away from being a fully operational unit. Let me know if you are still looking for one and I will figure out what I need out of it to cover shipping, etc..