B side fuzz schematic mismatch??

[Untro]

So i just finished, i thought, a bside fuzz. But lo, it doesnt work as intended, the trim knob does nothing at all. Passes signal, other functions work, the eq sections and volume work, but it sounds almost exactly like my usual signal and the trim knob does nothing. Very odd cuz i had made one the other month, and i had a second pcb. Nothing felt off about the build, it was easy and quick.

But now what im really flummoxed on: when i go to the pedal pcb build docs, it doesnt look like my pcb. The footprint is different, and 98% of the parts list is the same except like a 100nf cap that doesnt exist in the current one. So i dont really know how to go about troubleshooting without identifying parts. Ive already replaced the b25k trim pot, which didnt help unfortunately. Done some ground chasing, IC and pot seem grounded. Still not quite sure how to take ic pinout measurements

I know its bside fuzz, pcb030, and the weird thing is i built one already and dont remember this discrepancy, but that also came together quick and easy and i loved it. I wasnt even gonna test this on the rig but figured aw hell why not. Dang.

Any help identifying the issue or the original schematic would be greatly appreciated, not quite sure where to go from here.

 

[Zanshin]

There’s a number on the other side of the PCB. What is it?

 

[Untro]

PCB030. B side fuzz pops up in the store when searched.

 

[jwin615]

So i just finished, i thought, a bside fuzz. But lo, it doesnt work as intended, the trim knob does nothing at all. Passes signal, other functions work, the eq sections and volume work, but it sounds almost exactly like my usual signal and the trim knob does nothing. Very odd cuz i had made one the other month, and i had a second pcb. Nothing felt off about the build, it was easy and quick.

Make sure you didn't flip R5 and R6, though I'm not sure which ones those are. You'll have to follow the traces.

 

[Untro]

Make sure you didn't flip R5 and R6, though I'm not sure which ones those are. You'll have to follow the traces.
View attachment 76366

Totally, i figured theres something wrong with the 1st op amp gain stage. But how will i find r5/r6 without an accurate footprint layout? I feel like im just shooting in the dark. I verified that the pots are working, but it feels like its just set to a natural ‘no gain’ setting, like maybe leg two isnt feeding back into 1 like its supposed to?

 

[jwin615]

Totally, i figured theres something wrong with the 1st op amp gain stage. But how will i find r5/r6 without an accurate footprint layout? I feel like im just shooting in the dark. I verified that the pots are working, but it feels like its just set to a natural ‘no gain’ setting, like maybe leg two isnt feeding back into 1 like its supposed to?

Follow the traces on the pcb vs the schematic.
R5 connect pins 1 and 2
R6 is the only thing attached to C3, positive side. You can also use you DMM of resistance setting and look for zero ohms between those points.

 

[jesuscrisp]

You have 470K in both 470K and 470R spots which I assume is the issue.

 

[jwin615]

You have 470K in both 470K and 470R spots which I assume is the issue.

I figured it was o e of them off or inverted. Too tired to read all the resistors vs BOM.

 

[Untro]

Oof thanks, i poured over the BOM but i got flustered by the footprint difference. By some miracle i was able to fix it, and now it works great! Thanks for the help guys.