Thanks everyone for the input.
I contacted John Hesselberth. He said "Max corporation no longer exists. The founder died 10 or more years ago and his son liquidated the remaining inventory. Your only hope is to take it to a repair shop that works on DC motors and hope they can repair it for you."
I believe that the motor is working fine, but that the issue may be the control box, possibly the transformers. I was thinking of replacing the transformers, but they have no information on them. All the wiring and the circuit board looks fine, no overt signs of damage just old. I was going to start testing all the individual components, but may be the simplest thing to do is to find a new speed control box that is compatible. Any advice on a new speed controller?
Here what's on the control box:
The Max Wheel
0-200 rpm one hp 12 amp max
105 -125 VAC 50/60 hz
Model No. 1500
Serial No. 709-15463
Here's what is on the gear box:
Class I RATING FLEXALINE 1750 apm
Model No. BM01786 Serial No. UP
INPUT HP 1.27 RATIO 10 to 1
No specs. on the DC motor