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Model 2220 adjustments

Jailtime

Jailtime

Standin' on a corner
Here's a picture of the amp board in my 2220, i'm interested in the 4 trimming resistors at the top of the board (R730, 724, 729, 723). What do they adjust and where are the test points for them? There's a schematic in the Marantz database for the 2220, but I'm not much of a pro at reading them. :no: Can anybody figure out the 2220? I'd like to give some adjustments a shot, because the power amp is good as far as I know. :thmbsp:
 
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One on each side is for controling dc voltage and the other is for setting transistor bias current.
Without SM I'm not sure about the measuring points.
Those jumpers sticking out could be voltage test points but I wouldn't turn anything unless I was sure it was the right one.
Check the schematic and see what the pots are hooked to .
 
Without knowing the specified bias, I wouldn't attempt the adjustment.
DC balance is usually set by adjusting for equal positive and negative clipping of a test tone while observing the output with an O'scope. I think it's time to find a service manual.
Tom
 
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