Hi there! I have a Panasonic SV-3700 that is driving me crazy. Call it Machine A. Sometimes the transport won't move, but if the tape is exercised in Machine B, then it will play in Machine A, for a while. I have replaced the brakes, tension arm and pinch roller, which seemed to give relief for a few months, but now the problem has returned.
— Wes (via Internet)
I too have periodically entered the Panasonic twilight zone, but each time I have managed to escape, with just a few less brain cells. Just when I think I can repair anything these machines can dish out, along comes a batch that makes me feel nearly clueless.
There are a series of possible answers requiring a reasonable amount of research on your part. You've done most of the obvious work, but how old is the machine? Is it pre-’94? The first three characters of the serial number tell the story. “AA4” means 1994. Then look at the case. Is it textured (all machines up ’til late-’94) or smooth (late-’94 and after)? If pre-1994, then did you cut the PCB trace on the servo board? (As per details at www.tangible-technology.com) Have you ever changed the mode motor?
What kind of jamming is occurring? Is the left guide hanging up on the tension arm? Have you measured the tension? Does the right guide seem to be stuck in the “loaded” position? These are but a few of the questions you should ask yourself.
The first things I look for are the stainless steel “locating pins” at the head of each slant block/precision guide assembly. They are supposed to be press fit, but many come loose. Replacing them is a bear. All service issues ultimately come down to how much you are willing to spend.