Marantz PM-75

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Servicing notes

(Main amp board)

Remove all old glue around large capacitors

Replace/Check all capacitors with 105c high temp, other boards seem ok

Service manual online is wrong in a few areas, possibly some different versions

if can't get full power and turns off relay at 40w then connect QN01 (E) (emitter) to ground with 1k resistor 1/4w (heat sink around it etc) then it will do the full power, 120w 8 ohm 180w 4 ohm 1kHz RMS. (closest ground is the 3 pin power connector)


Idle current is wrong in the manual, there is 6 pins on the main transistor side connect to edge to middle (closest to edge) (eg 1 to 3 and then 4 to 6) and then same for the other side, like a normal amp, 7mV.

Normal to have about 80mV DC on the speakers.

Excellent sound quality once finished

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