I modified the AC motor, belt drive lathe to replace the DC motor on the treadmill and the control board to drive my lathe directly so I have stepless speed control. I've found that if I turn the motor off with too much load, the motor will try to draw DC endlessly. This will overheat the control board and trip the 20 amp AC switch on the control panel. I put a 15A DC thermal switch in the motor power line and that fixed the problem. Now all I have to do is restart the treadmill motor when this happens. Problem solved.