MRC Tech II problem

[Harley-Davidson]

I´ve an old MRC TECH II 2400 DC controller. Some locos, specially with 3 poles motor, make a noise, a vibration (no pulse applied), not seen when locos run with other DC controller. Anybody knows what happens? Thanks

[ATLANTIC CENTRAL]

I don't have a schematic on the exact circuit, but I do believe from previous experiance that the TECH II line are all transistor motor control circuits, which almost always have some degree of "pluse" built in.

And, a three pole motor is very likely to be noisy at slow speeds on this type of throttle circuit.

Sheldon