Ok! So I think the hard part of this machine is over. I managed to clean everything and get the belt on without breaking the flex cable. The nylon parts of the table reels have been pushed together, there's still a bit of chatter in reverse but less than before. New pinch rollers have been installed and I didn't even lose the ball bearings. Only one major problem remains. When FF or RW is pressed there is absolutely no movement from anything at all in the machine, and if I press them I can no longer play in either direction unless I open and close the door. Looking at the motor that moves gears for fast winding I can't see anything visually wrong but I also didn't remove each and every gear because I didn't want to press my luck. There is absolutely no movement from the gears if I try and turn them by hand, but I am pretty sure that's normal. Unfortunately I have no way to power the motor outside of the machine Is it possible I've missed a switch somewhere? I don't think it's likely that both buttons are broken. Any advice is appreciated. Thank you!
Fact once you press FF/REW, the other commands no longer work suggest the logic control side does register that command. Buttons being both faulty is very unlikely indeed, even more so given the above thing. Since the transistors driving the 2 logic motors are on the potted hybrid module CP801, there's not much you can check apart from the voltage getting to these motors. You can solder 2 wires for measurement, however FF/REW should at least try to start even with the reel assy removed. Just have that white wire on back of main PCB soldered.
Thank you for the info! Unfortunately voltage doesn't seem to be going anywhere on the unit right now. I must have made a mistake when reassembling it and introduced a short somewhere as the negative terminal got hot and now nothing much seems to turn on. I believe I may have fried the dc-dc converter section. I'll continue poking around it, but I've got a feeling its beyond my skills to repair at this point.
DC-DC converter only powers the Dolby circuits, so even if that's fried (which I doubt) it wouldn't explain the symptoms. Most likely it's something simple like a + wire touching ground. Happened to me once that battery wires got hot, but can't remember what the problem was (but was simple).
Interesting. I only thought the DC-DC converter was faulty because the values I was measuring didn't match the service manual, but that makes sense if the machine is off / dolby isn't on. The only wires I really touched were for the motor, battery terminals, and that top board with the controls, but it may be worth re-flowing them in case I made a mistake in there somewhere. The short does seem to be solved, batteries / terminals are no longer getting hot, there's just no response from the machine.
