Thanks for your reply, I read it back a good few times on Sunday to try to break it down and understand how the GEC board works, but no unfortunately I have no info on this at present. Indeed my board does appear to have similar connections to your Sprint board although the layout is different.

I’m up for trying the “switch & pot” although I have no idea what a pot is, haha. I won’t be able to try this until next week however as my schedule for this week is pretty crammed

In regards to the two other boards you asked about, the small one is a relay board. It feeds relays 1 and 2 for the motor direction. If the other board is a PWM generator that might explain what my next step is within Mach3 > Ports & Pins > Spindle Setup

Also, I’ve just picked up an old Denford Starmill from a friend so that’ll be the next project once I get the TCL running :)