I dismantled a Keys Fitness treadmill, traced out the motor controller circuit, and deduced its operation. Unlike the MC-60 and older Minarik controllers, which are AC phase control configurations arranged in a bridge circuit to drive the DC motor, this one is a PWM configuration driving the motor from a high voltage DC link. The attached document describes the circuitry and its operation. Perhaps it will be useful to some reader.

CAUTION - voltages on the board can kill you. You have been warned.

Mike

 

Thanks for that, should help alot in the future!
Max.