I'm working on a Fender Twin Reverb 135 ultralinear with the pull-out master volume. I can follow a 1kHz sine wave up until the left leg of the master volume, where the two 220k resistors meet, and then it disappears after that. If I disconnect the wiper from the rest of the circuit, the signal will show up at the wiper, and I can very the amplitude by turning the pot. But reconnect the wiper to the circuit, and it vanishes again from the wiper. I've checked all of the resistors, all of the caps in this portion of the circuit are new, and I've tried different 12AT7's for V6. Running out of ideas. . .
