Thanks Harry and Technicsplayer for your latest comments
Harry the tests you suggested are OK .

Technicsplayer we will try out more extensive tests when my friend can assist me
Yesterday we downloaded the service manual.
I am a retired Motor mechanic and know how useful a manual is.
Unfortunately I don't understand electronics but with help we have been able to make some progress in some tests

Seeing others haven't experienced our problem we will have to be patient.

Dave L.