The original treadmill circuitry.
I have and tried a commercial DC drive but the original treadmill unit runs the motor much better and I decided to use it. I modified it, getting rid of all the extra functionalities retaining only four inputs, via momentary pushbuttons, to the control panel. The control panel feeds the power unit via separate cable and I cannot figure out how it controls the power unit. I want to replace the speed UP and DOWN pushbuttons with a pot, for a faster operation but here my electronics 'expertise' is at its limits. I tried applying 5 VDC at some points where I suspected the power unit gets its inputs from the controls, but it made no difference, and did not wreck it, either...
I can get the parts out of the enclosure and check the numbers but I tried to find out the details while building the sander and did not find any specific info like schematics etc.