rather than start a new thread,,,
I'm repairing a Marantz PM-66SE KI signature and have indeed repaired it, it works! however the right side has no bias voltage at all nor can it be adjusted the left side is fine and can be adjusted. The right heatsink remains cold so where could the fault lie? I've tested everything I can think, could the small variable pot itself be faulty? it seems to move properly.
I'm repairing a Marantz PM-66SE KI signature and have indeed repaired it, it works! however the right side has no bias voltage at all nor can it be adjusted the left side is fine and can be adjusted. The right heatsink remains cold so where could the fault lie? I've tested everything I can think, could the small variable pot itself be faulty? it seems to move properly.
Post the part of the circuit showing the pot and output stage. Without having the circuit in front of me......
The voltage across the vbe multiplier transistor should increase smoothly as the pot is turned. A pair of drivers and a pair of outputs means you need around 2.7 volts to begin to get the stage to conduct.
Compare voltages across the multiplier with the good channel.
The voltage across the vbe multiplier transistor should increase smoothly as the pot is turned. A pair of drivers and a pair of outputs means you need around 2.7 volts to begin to get the stage to conduct.
Compare voltages across the multiplier with the good channel.
It might if the image you attached was legible. Have you tried using the snipping tool?
So what is the voltage across the transistor the pot is wired to ?
The 2.7v I mentioned above would be wrong for the circuit you show because there are pre drivers, drivers and outputs. That means around 4 volts is needed before the output stage would draw current.
Also check the voltage across R722 and compare with the good channel.
The 2.7v I mentioned above would be wrong for the circuit you show because there are pre drivers, drivers and outputs. That means around 4 volts is needed before the output stage would draw current.
Also check the voltage across R722 and compare with the good channel.
I doubt that alone would cause the problem you have however if the resistor is genuinely high in value then that suggests some other issue has occurred.
All the clues will be there in the form of the voltage measurements. If you can get up to 4 volts (or higher) across Q751 then the outputs should start conducting heavily. 2.2 ohms to 6 ohms won't significantly alter that.
All the clues will be there in the form of the voltage measurements. If you can get up to 4 volts (or higher) across Q751 then the outputs should start conducting heavily. 2.2 ohms to 6 ohms won't significantly alter that.
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