marc is correct, if you are trying to repair a transistor inside the controller you will have to source your parts locally or some other means. Komatsu does not provide individual parts for thier components like the drive controller, no other mfg does either far as i know. Your only options are to send it off to be repaired by a company such as flight systems or source the parts you need yourself.

IF your lucky just replacing the transistor alone will fix it but no guarantees because there may be other parts such as resistors or diodes in the circuit that may be blown as well.
Its generally a good practice to just replace the component instead of trying to repair it. The labor time for repair over replacement is usually excessive so most tend to just replace the part.