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NAD 302 stereo balance problem

In order to get equal output from both L and R channels, I need to set the balance pot fully left. The left channel is considerably down on gain, the right channel appears to be operating normally.
To get equal output on both channels requires the balance pot to be turned fully left and the main volume to be turned up quite a bit to compensate.

I've checked over the PCB for obvious signs of component failure and nothing jumps out at me. Q507 and Q508 have been getting hot, as there is some discoloration on the PCB around these components, but no sign of any overheating damage to resistors.

The balance potentiometer itself seems to operate well, no dry joints around it. Tried swapping speakers over of course to verify it's a problem with the amp, and tried differnet phono cables from differenet input sources too.

Any ideas ?

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I would replace the output transistors of the bad channel and any very low ohm resistors associated with them.
Whilst youre in there replace the electrolytic caps in the power amp section. Caps are cheap and plentiful.
I dont know what the rest of the circuit looks like but there might be a need to balance the DC offset after replacing transistors.

matelectronics.com and audiolabga.com carry many good replacement transistors.

Posted on Dec 30, 2008

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