Leeson makes controllers for both permanent-magnet and shunt-wound motors.
Shunt-wound is required for 4-quadrant, or "regenerative" controllers that perform active braking (applying reverse torque) for speed regulation. Since the device isn't intended to slow horses down, I'm guessing that Dnk has got it right, and it's a 90-volt PM motor with just two wires.
I'm also guessing that the controller is the 174308, which has the switches and pot built into the NEMA-1 box, in which case it's really hard to imagine a fault condition that wasn't cleared with the replacement of both the controller and the motor. But then, stranger things have happened, so I would:
1) Check that the wire to the CCW pin on the pot is not broken, and
2) Clip a DVM across control board pins S2(+) and S1(-) and check that the voltage varies between 0 and +1.4 volts over the range of the pot.
3) Obviously, check that the "MIN SPD" adjustment is full CCW (zero).
4) While you're at it, see if turning the "MAX SPD" adjustment down reduces the speed at all.
I'll have to agree with mxslick -- If everything else has been replaced, the wiring is all that's left. One possibility is that there's a leak to ground on one of the motor wires, which could have two effects:
1) Depending on the controller circuit design, it could effectively bypass the SCR control. Hint: Does it also run too fast when reversed?
2) If the controller is very clever, it measures the motor speed in the off-time between drive pulses by measuring the open-circuit voltage it generates. Leakage to ground on a motor lead could result in an under-speed measurement, and the controller would apply more torque to compensate. This is also how a motor that's "going bad" can fool the controller into running it too fast.
As a test, I'd consider disconnecting the existing wires and run a temporary 2-wire cable directly from the controller to the motor. (How far is that, by the way?)
Please post the controller and motor model numbers if you've got 'em, and good luck.
