Crate GX140C preamp problems

[Tone Meister]

I have a GX140C, and both power amps work when injecting a 1K signal to the FX loop line in. I have also patched a jumper cable from each of the the FX sends to FX return and get no throughput. I realize the return is stereo and uses a TRS connection, and I also realize the loop has both mono and stereo sends.

I can inject a signal to the front panel INSERT jack and get throughput to BOTH amplifiers. When the signal is injected into the main INPUT, I can trace the injected signal as far as the way to C34 and R31 Level pot, then lose it.

-Stan

[Tone Meister]

I'm still trying to find a schematic and would appreciate it if anyone has one to upload.

Thanks!