treadmill controller question

I am new here , so I have a lot of reading to do. I have a free treadmill that I want to use the motor on my 3 phase milling machine. I graduated in automotive engineering and later worked in electronics manufacturing, mostly on the assembly and mechanical side. The treadmill starts for a few seconds then gives an error 41 code. I want to modify the pcb and add a speed control pot. The Pcb used a l622f rectifier, 6 pins with 2 g terminals. It's rated for 42 amps. more questions later after I try to draw a schematic of the pcb.