Hi Graham
Sounds like a cracked PCB or damaged power pin. I am electronics (Avionics) and camera trained (although Aircraft cameras) and can look at it for you but cannot guarantee anything. I have necessary variable power supplies to check it out and I repair Gemini1's to component level so handling it is a cinch but finding the issue...well it's up to the electron gods.
It's up to you. PM me if you want me to look at it.