Anyone familiar with the protection/ op relay cct? Would seem to monitor the junction of 2 resistors fed from each channel output. Pink, Rch, 47K Purple, Lch, 56K Why unequal? all inside looks original Monitors for any sustained DC, clipping or excessive ac or all 3?
The pair of 1M resistors off the outputs are feedback into the amps via IC1
Can't say this necessarily applies, but Yamaha uses different value sensing resistors so that in the unlikely event of opposite DC offsets at both amp channels' outputs, the protection circuit won't be "fooled". If you had +50 volts at one amp output, and -50 volts at the other, the protection circuit would not trigger, and you'd have two blown speakers. Maybe this logic applies here.
Mark Z.
sensing
I'd not thought of that, it makes perfect logical sense now
sensing
With this amp +/-44V so 4Vdc maximum available in that worse case, 3.1V if following impedance is 100K and still 1.1V if 10K impedance
-- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on
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