I plugged the computer in and it immediately started popping and smoking! Suffice to say I think the BBC B is dead. I have a bit of time tomorrow so will power the control box and see what I can find.

I found this on another forum https://www.cnczone.com/forums/gener...78836-cnc.html

Seems to think I can attach a pot to 10, 11 & 12. Not sure what I have to do to the INH - assuming that is inhibit and INH (h) means that it is inhibit when pin 8 has 5v then presumably if it's disconnected then it should run - or maybe I am over simplifying!