Thanks Hugh.The short answer is 10.
However, a couple of days ago, I got a chance to go further in my investigation. I unplugged and reconnected each of the connections to the PCB and then added 12V. Voila, action! It seems my problem had been that something had moved just enough to break the circuit. Duh!That evening the sky was clear (first time in what seems like months) and the mount worked perfectly. All I need now is a few more clear nights to reassure myself that I have indeed solved my problem
Cheers,
Jeff