i originally wrote
"While I will report back to the forum in full I will just note that several weeks ago I had what I thought was a tape head clog which manifested itself with horizontal drop outs. The service engineer carefully cleaned the tape path and realigned the heads. The problem appeared to be fixed however out on a shoot it re-manifested itself. I returned the camera to the service company who repeated the procedure and checked the camera again. Again I took it out on a job after testing it myself and again the problem occurred.
I returned it again to the service company who contacted the factory in Japan who recommended that a particular component in the power supply be replaced with a component of a different specification. That has now happened and I received the camera back and tested it last night with a good result. However since the fault appears intermittent I will reserve judgement for another week or so."

Bad news, after two outings the fault reappeared, back to the service engineer, it appears that the intermittent fault is probably due to a small component (one of hundreds) on one of the main boards, and it is down to trial and error to find the faulting component.

regards
Ian Skurrie