HR Deville problem....?

[acorkos]

The amp powers up, but no guitar sound from either clean or drive settings....just slight hiss. When I plug a guitar cord into the power amp in jack...nice loud sound. so the power amp is OK.

i can trace the signal from the input jack to pin 2 of v1...but nothing at pin 1 of V1. i tried 3 different tubes....no change. i resoldered all the contacts on the V1 PCB (socket + ribbon connector wires) and tightened the tube pin sockets...no change. no cracks or broken traces on the V1 PCB.

The 100K plate resistor R4 has 397 volts on the power supply side, 394 volts on the tube side. R11, the 100K plate resistor on pin 6 of V1 has 265 volts on the tube side.

Cathode pin 3 of V1 has .007 volts DC on it...schematic says 1.97V. Pin 8 of V1 has 1.97V on it.

I pulled the main PCB, replaced R4, and resoldered the solder joints at the V1 ribbon connector (main PCB side). no change.

I don't completely understand this stuff, so there may be something obvious I am missing. Any help in conquering this will be greatly appreciated.

[MWJB]

The lack of voltage drop accross the plate resistor at pin 1 is suspicious (you should be dropping 130 odd volts accross this), as is the low cathode voltage.

Check the ground reference & value of the resistor at pin 3, check the cathode bypass cap isn't shorted.

Double check R4 value, you wouldn't be the first person to accidentally sub a 100K plate resistor with 100ohms.

[acorkos]

Originally Posted by MWJB

The lack of voltage drop accross the plate resistor at pin 1 is suspicious (you should be dropping 130 odd volts accross this), as is the low cathode voltage.

Check the ground reference & value of the resistor at pin 3, check the cathode bypass cap isn't shorted.

Double check R4 value, you wouldn't be the first person to accidentally sub a 100K plate resistor with 100ohms.

thanks for the reply

ground is intact at the cathode cap/resistor, and the cap is not shorted. verified 100K on the plate resistor with my meter.

i'm a little suspicious of the socket...i 'm going to check pin continuity from the tube side to the PCB side.

EDIT: Yup, pin 1 is broken inside the socket....no continuity from tube pin to PCB