Have a failed Reliance "Jr. Pak-1000" 0.3KW DC motor drive. Note that this is not Reliance USA, as in Rockwell, etc., but Reliance, Japan, which used to be part of Reliance Int'l, but no more.
Symptom is that dc motor is not running smoothly at low speed setting (motor "jerks"), and doesn't reach top speed. Swapping motors and controllers indicates this controller is at fault.
It consists of 3 basic components: - a PBF206 thyristor "H-bridge" - a 25cm^^3 cube-shaped module These two modules are in series with each other and with the load and the230vac mains.
Controlling these modules is a PCB which accepts a small (0-8vdc) speed control voltage and a speed-proportional feedback tachometer voltage (0-100vdc), and outputs control signals (via small conductors/molex plug) to both modules.
The "mystery cube" is marked with simply "MC-0005G". No source logo or icon. I can't find any reference to such a part. Any help would be greatly appreciated.