What I have is an old Rigid Pipe Threader unit 535 series. My original problem with this was that it was tripping the breaker. After doing a few quick checks and found nothing really wrong I took the motor out to find the Stator windings had arced and had a short. Thinking this was the problem I ordered a new field, bearings, brushes and brush wires would solve this issue. After reinstalling the motor to give her a try there was some sparking going on the commutator between the brushes and then 10 seconds later a tripped breaker. Now this obviously is now pointing to the armature and com but is there any thing I can do for testing before I order a new one or at least learn something for the next time.