Chop Shop Troubleshooting

J

jrhevron

Active member
HI all... I build a pedal or two a year, so I'm by no means an expert, but not a total noob.

I just put together a Chop Shop/Barbershop drive. I populated the board with components from smallbear and reused a power jack and in/out jacks from an old build. Got it all set... and no signal... signal on passthrough/when footswitch off. Pots do nothing and trimmers show no voltage and don't change anything.

I went through and probed and audio signal seems to be going all the way through, just no effect. I am having a voltage issue. I get 9V at R100 but no voltage at the trimmers/pads or at R11 or Q3.

I've reflowed and took the switch out just to make sure that that isn't an issue.

Any ideas on what to do? Clearly seems like a voltage issue... something is killing it after R100, I guess?
 
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I think that part of my question is how I would go about following the voltage path based on the schematic. Clearly, it seems like the voltage is dropping somewhere or being shunt or not grounded. I know how to follow the audio signal, but it's less clear on the voltage path.

Actually... took another look at the schematic and it's clearer to me now.
 
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@Robert I did more testing and was able to trace the 9v through to the end. Not sure what the issue was before.

Still, the pedal isn’t working.

I did an audio probe and found that the signal dies at C4. It makes it to the jfet—one side—and then doesn’t show up at either of the other poles. I do get continuity from C4 to one of the other jfet legs.

I feel like the issue has to be in this area, but I’m all out of ideas. I replaced the jfet and reflowed everything.

Any other ideas? :)
 
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