Perhaps spoke too soon but we are close.
The +15v bridge rectifier is running at scorching hot and the -8 and +5v are not far behind.
this was the initial finding when I had first fixed the scope way back when...
The trace disappears after maybe fifteen minutes and only half appears with the beam-finder there-after.
I'm off to bed, and shall have another look in the morning, but we definitely still have a detail to resolve.
James55