Gibson GA-20T Channel 2 dead

[BigE]

working on a Gibson GA-20T.  The second channel is Dead.  I can trace signal to the input of the 5879 but nothing out.  Just sounds like trash.  I did notice however that if I pull the 6SQ7 I do get a small signal (not what it should be) out of the channel.

Only thing done so far is changed filter caps.  Also tried new 5879 and 6SQ7 tubes and no dice.  Here's my voltages on the 5879:

1:  .01
3:  1.3V
7:  0V
8: 163V
9:  1.35

schematic here:  http://schematicheaven.net/gibsonamps/ga20t.pdf

thanks in advance for any suggestions...

[sluckey]

Pin 7 is the screen grid and should have a healthy positive voltage. Check resistance from pin 7 to ground. It should be about 150K, but I suspect that .25? cap is shorted. Change the cap if the resistance reading is not approx. 150K.

[BigE]

so I dug into it tonight.  Had Channel 2 passing signal by replacing the 1meg and the 150k resistors.  Wasn't as loud as I thought it should be but it's a start.

So next I was on to the trem that was dead.  Replaced the 3  .05 Caps in the trem and I can see the voltages swing on the 65Q7, but now the channel 2 is dead again.  Here's my current voltages on the 5879

3:  1 V
7:  25v
8:  107V
9:  1v

Is the tube not getting enough voltage on pin 8 to turn it on now?  Possibly need a new 510k plate resistor?

thanks again...

[HotBluePlates]

What kind of caps does this thing have in it?

Between the 5879 and 6SQ7 plates are a pair of 510kΩ resistors and a 0.01uF cap to ground. What happens if you unsolder one side of that cap?

[BigE]

I put new filter caps in it.

Pull one end of that cap and no change.   Still dead...