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Well you have been busy ..I was hoping one would be faulty..finding it hard to navigate to the end of this thread perhaps soon should summarize the main facts and start a new post with the schematic and a top & bottom photo of the board seeing I don't seem to be able to narrow down to the fault.
The fets won't cause DC at the output so I'll leave that for the moment they have a source, gate and drain like a flock of sheep running from the source to the drain and the gate can stop them... transistor has collector, base and emitter by altering the state of the base more or less sheep can run from the collector to the emitter... well thats a very very rough description dunno why I chose sheep.....
Two things I can think of we need to check 1. the emitter resistors and 2. the pre-amp low voltage power supply.
R55,R53,R136 & R126 These are 5 watt resistors and are wire wound and encased in a ceramic material as they are designed
to be able to cope with heat. Sometimes referred to as cement resistors. They are only 0.33 ohms so will show as a short
circuit or 1 ohm'ish unless you have a mega expensive low ohms meter.
If one of these goes it upsets the see-saw and one of the supplies leans in and puts dc on the output..again very rough
inaccurate description
While you are there check the driver emitters.. as they are only half watt they are more likely to "burn" ie become discoloured
while going open circuit they are 330 ohms (orange orange brown) 47 ohms (yellow violet black) R54, R56, R135 & R134
Likewise check the 2 resistors in series with the collectors R118 and R44 (330 ohms).
Also better check the low voltage supplies +&- 15.5 volts. Anything between 14.8 and 16v is fine.
Measure it at c6 and c7 or between ground and pin 8 and ground and pin 4 IC 2 or IC 3 and if they are hard to connect to D6 cathode (the marked or "line side")
and ground (+15.5v) and D5 anode and ground (-15.5v). They are near the input.
The fets won't cause DC at the output so I'll leave that for the moment they have a source, gate and drain like a flock of sheep running from the source to the drain and the gate can stop them... transistor has collector, base and emitter by altering the state of the base more or less sheep can run from the collector to the emitter... well thats a very very rough description dunno why I chose sheep.....
Two things I can think of we need to check 1. the emitter resistors and 2. the pre-amp low voltage power supply.
R55,R53,R136 & R126 These are 5 watt resistors and are wire wound and encased in a ceramic material as they are designed
to be able to cope with heat. Sometimes referred to as cement resistors. They are only 0.33 ohms so will show as a short
circuit or 1 ohm'ish unless you have a mega expensive low ohms meter.
If one of these goes it upsets the see-saw and one of the supplies leans in and puts dc on the output..again very rough
inaccurate description
While you are there check the driver emitters.. as they are only half watt they are more likely to "burn" ie become discoloured
while going open circuit they are 330 ohms (orange orange brown) 47 ohms (yellow violet black) R54, R56, R135 & R134
Likewise check the 2 resistors in series with the collectors R118 and R44 (330 ohms).
Also better check the low voltage supplies +&- 15.5 volts. Anything between 14.8 and 16v is fine.
Measure it at c6 and c7 or between ground and pin 8 and ground and pin 4 IC 2 or IC 3 and if they are hard to connect to D6 cathode (the marked or "line side")
and ground (+15.5v) and D5 anode and ground (-15.5v). They are near the input.
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