Mild dilemma with low bias on one channel

[Sunnbobb]

Amp 1, the one I stupidly allowed the left meter to touch the buss bar, is finally back up and running properly, mostly. By mostly, I mean the only issue I have is the left channel bias adjustment only has a range of .21 to .33, the right channel has a range of .22 to .43 or so. I matched both channels up to .33 and everything seems to be fine. So, the question is, is it ok to just leave it at .33 or do I need to go further to get that bias up? I have replaced transistors and bias transistors in an effort to weed the problem out. I don't have a scope. BTW, this is a full comp wopl. Thoughts?

 

[laatsch55]

Got backplanes too?

 

[Sunnbobb]

Got backplanes too?

Yup, full boat. led board, backplane, filter caps, rectifier, output relay, yada yada,,

 

[Sunnbobb]

Going back and forth between the test points with a single multimeter gives me the results I listed. I used both a cheapo meter, an Ames DM1010, and for fun, the Triplett 630.

 

[wattsabundant]

Check the value of the resistors you're measuring across. If possible, run the amp into a resistive load until the heatsinks are very warm. Recheck the bias. The bias should drop as with increase in temperature and return to original value when the amp is idling.

 

[J!m]

Key word there: "should".

 

[Sunnbobb]

Check the value of the resistors you're measuring across. If possible, run the amp into a resistive load until the heatsinks are very warm. Recheck the bias. The bias should drop as with increase in temperature and return to original value when the amp is idling.

Testing between TP1 and Pad 9 shows 151 Ω as it should. I don't see a 10 Ω resistor like in the original PL backplane. I'll try warming it up and retest, thanks for the ideas. Ω