"b" writes:

whatever is driving the spools needs checking. my money is on a rubber
idler tyre which needs resurfacing with emery paper or replacing. you
will have to open the unit up and see what happens - grasp the take up
spool to see if there is much resistance in play. Motjon sensors may
need cleaning - look for a reflective plate under the spool or a reed
switch if the deck is old.

Thanks, Cliff and B. I think you're right. I think I posted a
follow-up to my own note saying that I did discover a motion sensor that
wasn't moving; when I pulled on it with my fingers, it started to work.
It still doesn't fast forward or rewind as quickly as I think it should,
but it's better.

I hadn't thought of the emery paper on an idler idea; I'll check to see
if that might work. I was betting on the belts.

Bill