Now this channel has 46V on the top of R29. The other channel is still at 37. Something is still off here. They are both dropping roughly .5 volts.
R33's dropping 1.12 volts. R32 is dropping zero. This has gone completely out of balance again.
This voltage is set by the voltages on D3, D7 LEDs (reference to ground). And those are set by CCS, based on Q1. Tail current is set by D2 voltage and R9 value. You can adjust R9 to have the same 37V at the top sides of D3, D7.
No idea. Not good contact somewhere? Op-amp plug? It can't just change. A completely self-balancing circuit...
The op amp is soldered in. I was kicking myself for that when I replaced it. The only thing original on this board is most of the resistors, the caps and the blue LEDs. I've got to have a wrong resistor somewhere or a solder bridge. I'm out of alcohol to clean the solder goo. I think I should take a trip to the drug store and clean this thing up.
Gunk's latest brake clean doesn't touch it any more. I found a vintage can of MG Chemical's finest. I can't see any cold joints I'm going to go through all the resistors again.
Maybe this is the result of "Q1 is starting to cook". Too much current through Q3 and so on. But neither Q1, nor Q3 are stressed. They normally don't even get warm, as you just said.
I think this has made a difference. Vas current is high. I'm wondering if Q1 was damaged from my high LED voltages and just failed. I'm going to change R29 and see how it works.
Now my VAS current is a little low but I'm over 38 volts at D3 and D7. DC offset is -20mV. Will adjusting R9 affect VAS current?
I've got R9 at 430R. That brought D3 and D7 down to 36 volts. I've got R20 at 150R Vas current is around 7mA.
As it warms up Vas current rises slowly, then creeps back down. I had it playing sine waves for 20 minutes and when I shut the signal generator off Vas current had fallen farther. Is this temperature compensating or do I have a resistor getting warm somewhere? The other channel seems to just warm up and level off.