This lovely example of 70’s Japanese workmanship came in with no output. Turns out +57V and -57V rail rectifiers (double-diodes D501 and D502) one had gone short circuit, and taken out both 2.2 ohm R501/R502 1/8W fusible resistors.
As these were now unobtainium (CO8P-1 and CO8P-1R) they were temporarily replaced with 1/8W and couple of 1N4001s to restore service to check, and we had lift off.
A more permanent solution was fitted to both rails once the fusible resistors arrived.
Then gave it a good clean underneath (including cleaning out those PVC insulating covers as seen below which had been leaching sticky plasticizer (ewww), collecting dust and a nasty orange/brown colour, they were clear at one time I’m sure.
Went through the alignment procedure for modular amps so they were getting the correct +/- 40V at TP3 and TP2, had 0V DC offset and the bias quiescent current was the correct 15mV (as could be expected, it had drifted quite a bit over the years) but now good.
Then found out the speaker select switches were dirty, and not even a liberal dousing of Deoxit D5 would remedy, so they had to come out, which necessitated removal of the front panel, including all the knobs etc, quite a task!
… they were then disassembled and all the tarnish cleaned away, before a protective layer of Deoxit was applied
Reassembled and tested all good, returned to owner.