DCC170 doesn´t work after belt replacement

I have had a DCC170 for more than 25 years. It has very little use and has been unused for more than 15 years. Six years ago I had to change the belt (0.8/64mm) and it worked correctly again. But a week ago I wanted to recharge the battery but I found that it was not working well. Powered externally and with a DCC tape inside, when you press PLAY, “POWER ON” appears on the screen, the motor and pulley rotate in one direction for one second, the PLAY screen appears, the motor rotates in the opposite direction for one second more and the “POWER OFF” screen appears. The belt was fine though, but I changed it again (0.6/67mm) and checked the proper functioning of the auto-reverse gears and black switch, and the actuation of the electromagnet for “FWD” and “REW”, even with a tape inside. I have lightly grased those parts. But when I put it back together the same problem appears again. The capacitors don’t seem to be leaking, and the switches seem fine. Has anyone solved this problem?

Hi and welcome,
It could be the engine, but for sure, the belt 0,6/67 is most likely, never going to work.
All replacement belts we found, with a 0,6mm will not work on the long run.

We currently use 0,7mm.

The 0,8 should work fine and if the player will not turn on, it could be the engine or a problem with a optical sensor, that indicates that the player is running.

Both sensors are places above the wheels colored silver/black on board 1. They are easy to find.

Thanks for your answer.
You have to take into account my description of the problem.
The problem is the same with the 0.8/64 belt and with the 0.6/67.
The motor and pulley rotate in both directions during testing.
POWER ON appears on the screen, then the PLAY screen and after 2 seconds POWER OFF and it turns off.
This means that it is not the belt, nor the motor.
The device has degenerated in six years without use.
I’ll look at the optical gyro sensors in case they are dirty. The rubbery coating gives off gases over time that make everything dirty.