Tag Archives: GEC Gemini

GEC Gemini motor controller is working

I got a Boxford TCL 125 CNC lathe a few years ago that I have been working on getting up and running. I gutted all the electronics except for the spindle motor controller, and replaced the stepper drivers and built a PC right into the lathe enclosure. I’ll post more on those upgrades later. All the new stuff I added is working fine, it is the old GEC Gemini motor controller that was giving me a hard time. But, after reading this post I got it working, it looks like I was just missing the kill switch connection.

So here are the connections to the big orange header:

  1. NC
  2. 0-8 VDC – This sets the motor speed
  3. 10VDC – Supply voltage for the controller
  4. NC
  5. NC
  6. NC
  7. GND
  8. GND
  9. Kill switch input – This needs to be connected to pin 3 for the motor to run
  10. GND
  11. NC
  12. NC

It looks like there are traces on the PCB that go to the pins that I have labeled as NC, but I’m not sure what they are for and the motor is working without them. If you know what they are used for leave some feedback.