Arthur- This is what I will end up doing when I have exhausted all other avenues, and it has returned to the top of my inbox.

Actually I lived for a large part of my life in a World Heritage area where these looms were invented. The designs were a guarded secret until an enterprising New Englander got a guided tour and memorised the designs until he got back to Pawtucket, or somewhere.

IanB- I chopped off the primary today and counted 460 turns (actually 920, but they are in parallel and can be ignored for voltage purposes).

The schematic showing the connections labelled 'AC27' cannot be correct as it would give 38VDC, and the reservoir capacitors for this rectified output are 35V working.

37 turns/460 turns x 240 volts =19 volts, which is 27VDC by coincidence, and more likely to have 35V capacitors, so maybe the Yamaha diagram has been mis-written.

This doesn't help with the main output as 280/460 x 240 = 146V which is 206VDC. The res capacitors are listed as 160 working voltage.

Or have I missed something? I ran a Dremel once round the toroid and each short piece of copper would be 1 turn. I divided the number by 2 as there are 2 windings, in parallel and in phase (unlike the secondaries.)

Regards, BT