Fuzz face trimpot doing nothing

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DingDong

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Hi, Noob here trying to breadboard first PNP Fuzz face. It gives sound and I even like it but the trim pot does not do anything. Q2 collector gives about -8.5V. It's really weird and Im out of ideas. Probably something typical noob stuff but can you give me some advice? AC128 as Q1 and Q2.

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There is jump wire between pins 2 & 3 under the trimmer.

Any ideas what is wrong? Thanks 🤖
 
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Robert said:
Some breadboards split the power rails in the middle of the board, any chance that's the issue?

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Oh my :D That was just about the kind of noob thing I thought it would be! Thank you sir 🫡
Now that it does something I still think there is something wrong. I can only change the voltage of Q2 between 8.9-9.5. I have no reference for what the voltage should be in Q2 collector but does that seem a bit high? In other schematics they trim it near -4.5V. I also lost alot of gain when I connected power rails.
 
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Not an expert by any means but wondering about the trim pot in parallel with R4? Could try pulling R4 and swapping the trimmer for a 50k. The "correct" bias is 1/2 supply voltage, or 4.5 but set it to what sounds good to you. If you haven't seen it JHS has an excellent playlist on breadboarding. heres the link for the one on PNP fuzz faces.
Good luck!
 
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Thank you everyone, I got it working and soldered it to perf board. I had many little problems along the way but now it works just how I like it. The weirdness with R4 and trimpot was my fault, the instructions said that I should remove R4 if using trimpot. In the end I replaced the trimpot with B20k pot to easily chance the bias. It's not the most beautiful and board design is just from my head but it was first ever not-a-kit-pedal for me and works so I'm happy!

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