I have a treadmill that was bought many years ago. I do not have the pack of information that usually come with it when it is newly bought. Its motor controller went bust. I do not have circuit diagram for it. By doing some simple measurements, I found the driver transistor IRFP460A was blown up. I replaced it, the motor would work but there is no speed regulation, when the motor is heavily loaded this transistor will burn again. The speed feedback link is done using a reed magnetic relay., which I checked ok.
I am hoping that one of you may have the circuit diagram of this controller to do proper repair of this pcb. I attached a photo of this controller unit.
I would imagine the original failure of the MOSFET blew up the driver chip / transistor too, or at least damaged it. Now the replacement MOSFET is getting a very dodgy gate drive (accounts for its tendency to fail).
Fault-finding with an oscilloscope is really needed - you could try replacing all the likely semiconductors on the board though. However this appears to be a circuit running at lethal voltages(*), so treat like mains (ie if in doubt don't take the risk).
The original MOSFET could easily be replaced by a higher spec one too.
(*) The IRFP460A is rated at 500V