Reynor Commercial Garage Door Opener

We have about 15 to 20 of these scattered around the shop and are having a problem with 2 of them that are wired together. These are old and made in 1979.
Model # RT311-1465SR
Serial # 572133
I am not getting power to the switches on the wall. The openers will work with the manual buttons inside the box (by the motor) but not at the open/stop/close switch. I am only showing about 6 volts to the switch while all of our functioning switches are receiving around 29 volts at the switch. These openers seem to be pretty bullet proof so it must be an internal component. Any ideas on what and how I could diagnose this problem.

Thanks, Robert

Commercial machines have a transformer inside that steps the power down from 115/220/480 to 24 volts. Sounds like thats your problem, you can test the the low side of that transformer, just BE CAREFUL, if its an industrial machine with a 480v supply you dont want to be playing around in there it would be deadly.