The Nexstar mount repairing attempt failed, so I removed some parts inside, hope that someone will find them useful:
The PCB, it's not functioning properly, I tried to fix it but failed, maybe some chips are still working?
The motors, they works perfectly, since the ALT circuit of the above PCB still works, I know the ALT motor works. Then I swap the ALT circuit to control the AZ motor, and it works, too. So, I know both motors work perfectly. They're very nice Pittman motor with encoder.
ALT and AZ gears, telfon washer, bearing, etc:-
The hand controller:-
Finally, this is the chip which I tried to replace for repairing, but after replacement, the issue persists. The chip is ordered from Mouser, I soldered one on the above PCB, one is left unused:-