SOLVED No Sound From Integral Preamp

[bhcarpenter]

Alright, after going over this repeatedly, I could sure use a second set of eyes. Bypass is fine, but I get no sound when it is on, except for a bit of a “blip” if I turn the volume all the way up and hit it hard. With a probe, I can hear a (distorted) signal going into pin 2 of IC1, but nothing coming out of pin 6. Already tried swapping the IC.

Voltages:

Vcc: 31.6v
Vref: 17.6v

Q1c: 0v
Q1b: 0v
Q1e: 0v
(From the schematic, I think this is expected)

Q2c: 22.0v
Q2b: 2.4v
Q2e: 16.8v

IC1
Pin 1: 0v
Pin 2: 22.0v
Pin 3: 17.6v
Pin 4: 0v
Pin 5: 0v
Pin 6: 1.4v
Pin 7: 31.6v
Pin 8: 0v

Anything look off to you all? Many thanks.

 

[bhcarpenter]

Hrm, that Vref seems high…

 

[carlinb17]

Have you cleaned off the flux?

 

[bhcarpenter]

Yeah, although I’ve resoldered a few things since the

 

[bhcarpenter]

Hrm. Still no luck. I guess the next thing to do is pull the caps after the opamp and check their value?

 

[fig]

Check the values of R103/R3. Doc calls for 1MΩ. Yours appear to be 160kΩ?

 

[bhcarpenter]

Holy shit Tayda gave me a bag of one hundred and fifty 160Ks labeled as a bag of 1Ms. I’m going to have to go back over every build I’ve done in the past 6 months (with the wife’s help, as I’m colorblind). Thank you @fig!