Obsidius Preamp - Issues with Attack switch

[Were we brave?]

Hey guys,

I'm having issues with the Attack switch on my Obsidius build. The cut and flat positions sound fine, but if I put it in the boost position, I get a super harsh distortion, like a bad bias or something. I couldn't find anything wrong with the part values in that area. Does anyone have any idea what it could be?

Here are my voltages:

DC In: 9.36v

IC1:
1: 4.53v
2: 4.53v
3: 4.11v
4: -
5: 4.52v
6: 4.54v
7: 4.54v
8: 9.08v

IC2:
1: 8.37v
2: 3.18v
3: 3.18v
4: 8.37v
5: -
6: 8.37v
7: -
8: -
9: -
10: 8.37v
11: -
12: 8.37v
13: -
14: -
15: 8.37v
16: -

IC3:
1: 4.77v
2: 4.53v
3: 4.07v
4: -
5: 4.10v
6: 4.54v
7: 4.54v
8: 9.08v

IC4:
1: 4:55v
2: 4.56v
3: 4.51v
4: -
5: 4.46v
6: 4.54v
7: 4.54v
8: 9.08v



Q1:
D: 7.69v
S: 3.07v
G: -

Q2:
D: 9.08v
S: 7.69v
G: 4.33v

Does anything seem odd or way off?

Thanks guys!

 

[Vildhjuggah]

referencing my thread that chuck helped me with
"Measure the DC voltage on IC2-3 and IC2-2 with no input signal. They should be equal (assuming you are using a good DMM) and somewhere between 2.5 and 5V."

"Lotta people have been having problems with J201s (as evidenced in this forum). Let's make sure they are happy. Check the voltage on Q1-1. Should be just above 4.5V. Check the voltage on Q1-2. Should be greater than zero."

"Check the voltage on pins 1 & 7 on the TL072s. They should all be near 4.5V. "

 

[Were we brave?]

Thanks for answering! I've double-checked the voltage on pin 1 of IC3 which read higher than the others; I got 4.58v, but it slowly creeps up to 4.77v as I had indicated.

As for Q1, I've swapped it with another J201 (this time SMD with adapter board) and the readings are similar. So Q1 should be around 4.5v? Hmm.