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Sansui Eight help - hum on one channel

Ok so you can now get the n and c voltages to be what they should be, is that correct?
How much is a lot?
 
Using the min/max/average feature on my DMM:

I'm getting 3.2V at N, swinging from 5.7 to 1.3V.

At C I'm getting -1.0, with 4.0V max and -2.9V min.
 
Thats odd, lets try the bias adjustment procedure, adj vr802 for .5 volts across r804. You may have to tweak vr 801.
Then measure between tp802 and tp803 and set vr804 for 0 volts.
 
Yes, so it is going to be a challenge to get it to 0.5V. It really moves around a lot, maybe it will be better at R804.
 
OK, done. Was able to get 0.5 V across R804 by just moving VR802. Set VR804 to zero between TP802 and 803.
 
OK now were cooking. Lets adjust vr803 for minimum voltage difference between c and n or maximum voltage at (o) referenced to ground, which ever is easier. This will set the bias current to minimum. What is the voltage you get after adjustment.
 
OK, was able to get the voltage difference between C and N to -2.1V. That was turning VR803 all the way counter clockwise.
 
Ok if point c is still close to 0 or slightly negative, lets put tr805 and tr806 back in. This should not change the voltage at point c as they should be turned off.
 
If you can set it back to -1 go ahead and reinstall tr807 and 808. If this is working correctly it should not be so jumpy and monitor h when you turn it on, should be approx 0 volts.
 
Put TR805 and 806 in. Was able to adjust C to -1. A bit jumpy, but not bad. N is reading +1.1V and slowly falling. O is reading zero.
 
Probably should recheck the vr802 setting with .5 volts across r804 and difference between tp802 and tp803 using vr804. Then recheck (o) for 0 volts approx.
If all that is ok, reinstall tr807 and tr808 and check (o) for 0 volts.
Seems like a long way around but caution is prudent.
 
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