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Marantz 2250 bias voltage

MartyGee666

MartyGee666

New Member
Hello!

I recapped a marantz 2250 and it's looking really good.

However, I'm getting some wandering bias voltage on one channel. Testing at points J710 and J708, one channel has a steady 8mA. The other channel however wonders all over the place & it creates a static over the speakers when connected. Not good!

The output transistors all test well, the pot that adjusts that voltage tests well. Transistors H710 & H711 tested well out of circuit.

My question is, where is that bias voltage generated? and/or where else should I be looking?

Thank you!
 
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Just this morning I was having the same problem in a Sansui. I began by taking all of the transistor voltages on the board in that channel to see where they were wrong.

Doing this I was able to find where I was losing my voltage so I began checking components in that area. I found the tiniest sliver of solder shorting a cap to ground. So small I couldn't see it with a magnifier. I knew my problem was in this area so I scraped between the contacts good. Problem solved.
 
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Thank you! I had a broken solder joint & it was causing the issue. Took the transistor out of circuit to test and then put it back in. Works like a charm now.
 
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