[samjmann]

If you measure from ground to any of the fuses for the 31 and 23v supplies you should be able to measure a low reading. If not, check that there is continuity between the reservoir caps for the same rails and the transformers secondaries.

If the tracks were o/c there must have been heavy currents, I would have thought it would have blown the fuses.

I see what you mean about the track layout and the circuit diagram, the ground tracks appear separate. Maybe there is a jumper link?

Sjm