Originally Posted by
RCaffin
I agree - check the brushes. They might be worn out, they might be jammed, or both. Imho, those motors are rather rugged and should survive a lot of mistreatment. You might also check the wiring and the driver - they are probably more likely to fail than the motor.
I will add that replacement Minertia UGFMED motors seems to be listed by various vendors and also on eBay. You may even be able to buy a replacement motor WITH encoder fitted. Mind you, adding an encoder to such a motor is very simple - they come in kit form.
Incidentally - you don't have to have an exact match for the motor. DC servo motors like that are very flexible.
Cheers
Roger