Kenwood KA-3500 bias needs help

[tusntuk2]

Hello again, just love this forum and the gracious help here! I just finished completely recapping a Kenny KA-3500, and the DC offset shows -6mv on one side and 56mv on the other. Not terrible, even if a little unbalanced, I understand, but when I check the bias it seems to wander from about 34mv to about 42mv. Again, not terrible, but I wondered if replacing the bias pots with something new might help? Would it also help balancing the DC offset? I've checked bias cold, warm, and warmer, and it wanders while I check it. Meanwhile, the amp sounds clean and musical, great detail and effortless power (well, what it has!) Any suggestions? Thanks, y'all!

 

[62vauxhall]

I've learned and come to accept that DC offset in old amplifiers will not be exactly the same in both channels. Maybe it wasn't even equal when brand new. Depending on who's giving the opinion, 56 mv is diddly squat - not even close to being enough to damage a speaker.

Bias readings will wonder as the amp warms up and should be set according to service manual spec after it's been idling a while like a 1/2 hour. No input or speakers connected. If the pots still provide a good even sweep - if it ain't broke, don't fix it.

 

[dlucy]

Have you checked the other ka-3500 threads here like this one: http://audiokarma.org/forums/index.php?threads/kenwood-ka-3500-bias-wont-adjust.731245/

 

[tusntuk2]

Thank you, Doug, I have. My amp was working fine before the recap, I was not having any apparent problems with transistors. I say apparent, but I am no transistor expert, and I did not separate and check individual transistors, only specified voltages in the schematic. I was concerned that the bias reading was not stable when I did measure it, even though it seems to be in bounds and the amp sounds very good after the recap. Didn't know if it might indicate a new problem. Today I'll run the amp for a few hours and let it heat itself up and check again. Thanks for the input! Jim