Gallien Krueger 1001rb schematic FOR PREAMP

[rockman627]

I had to change the volume and master volume pots. The old ones were difficult to remove and I may have nicked the pcb doing so. I can get sound out of the fx send jack, but nothing when I plug into the fx return. I would like to verify signal passes thru the master volume to the fx return. But although I can find plenty of schematics for the power amp, I can't find anything for the preamp.
Can anyone point me in the right direction?

[Kaz Kylheku]

Try including the preamp board part number "206-0251-A" in quotes when searching.

Another Gallien-Kruger amp uses the same preamp, evidently:

https://elektrotanya.com/gallien-krueger_700rb-ii_sch.pdf/download.html

Assuming that is correct, I can see that, as I suspected, the Return is a switched jack. If you are getting signal through the amp with nothing plugged into Return, that means signal is flowing through the connection in the jack. If you can't insert signal by plugging into the jack, something is wrong there. 

Like if the Return jack's switch is somehow not opening as it should, then your input has a low impedance path back to the output of the U5-A op-amp that drives Send.

Or do you mean that there is no sound out of the amp: but the last confirmed externally observable output where signal is seen is the Send jack?  I.e. the Return jack worked before, but you only touched volume pots; so the jack is probably fine.

[rockman627]

The amp made sound but the pots were noisy. Cleaning them did nothing, and the shafts on both pots moved in and out a little, so I changed them. I had to desolder, then really pry them out. Then there was no sound. I plugged a bass to the input and from the fx send to a Roland microcube . I got sound. Then I plugged straight to the fx return, no sound. I didn't touch the power board so I figure the problem is in the preamp board around the master volume area. The pot itself tests ok.