Hi Raymond,
When the pinch rollers disengage does the capstan stop too or does it keep moving?
When the reel tables stop moving but the "Play" button is still lit, try moving the reel tables manually. Is the resistance the same as when "stop" is engaged?
It sounds like one of the control circuits has a bad connection or maybe a capacitor that's going downhill. The reason I'm guessing that is there's a safety feature that should engage "stop" if the take up side (right) reel motor stops completely.
If you're lucky,.. it could be just an iffy connection. If you have any experience fooling around with electronics or have a buddy who is, you should try jiggling or pulling and reseating the multipin connectors that are on the two circuit boards located just under the capstan flywheel on the left and right. Do one at a time with the power off and check the machine.
Put a piece of tape to hold down one of the tensioners since you'll might have to do this a number of times for each connector.
Another source of weird speed problems could be the "speed selector, pitch control and timer" switches. Try switching and or turning each several times.
While you or your buddy are trying things it helps to think of these machines as just that,.. machines. Reel to reels are more closely related to a precision mechanical device than say, an amplifier (even though they have amps in them) and many problems arise from it's sitting unused (just like a Porsche in a barn). Things get gummed up, grease hardens and connections corrode.
Past those things, there's a lot of things it could be. Tired power supply components, a bad IC on the main control board etc. Either of which you probably will need a good tech to track down the problem.
