Machine is back in service, have repaired the power supply. Traced the circuits as best as I could , never got hold of a schematic. The fault was a number of turns short circuit in the HF chopper transformer.( the winding that feeds the +24 V rectifier) Took it apart and rewound it, after which a friend vacuum-impregnated it. Went thru all other components, found two iffy electrolytics also, replaced all 19 and revarnished the board.
Total cost for repair was around US$ 200.
Machine is now paying for itself!. A local sevice company had previously quoted US$ 6500 to replace the faulty power supply.
So, we got quite a hefty beer-kitty!