Thanks, Phil

Your advice on the capacitors is well taken, but I'm usually slow to replace parts unless they can't be tested.

The fault has recently become steady so that may help to resolve it. Someone long ago showed me how to test capactors using a meter. It involved switching leads and seeing the needle fall but I don't remember details like was the meter measuring volts or ohms, and if the cap is powered or not.

I may end up there, but as the fault is holding, I'm being optimistic and hoping I'll be able to trace the power to a definitive point. I'm sadly lacking in electronics, but in Art Benstein's drawing of the CB the caps seem to be only on the meter circuit. This very well be an incorrect assumption because that power then goes into the black ITT box, and I have no idea what that unit is even called, let alone what kind of mischief goes on in there.

Stay tuned,
Peter