I recently obtained a used Ham 4 that rotates fine but no direction indication. I'm used to cleaning or replacing the pot but this is different. there is no continuity between pin 1 and the wiper of the pot. it looks to me that the frame of the motor should be connected to pin 1(ground?) but it isn't. The brake works correctly and the motor runs correctly. How can it all work, except the pot and how can the frame not be grounded? I'm missing something simple I'm sure but I can't spot it. de K9DD.