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I built a PNP Marshall Supa Fuzz this summer with the Tagboard Effects layout. It worked but I was getting some scratchy sounds when using my guitar's volume pot. I wasn't sure if it was a bad electro somewhere, or it just didn't like the wall wart that runs my test box for populated PCBs.
So, I changed out all the electros and switched it to battery power. Now I am just getting a clean sound. What's weirder, it still works this way even if I remove all the transistors!
Any insight for me? Forgot to mention, the fuzz pot does nothing now and the volume pot no longer effects volume, it just makes the tone go from brighter to darker.
My guess is the footswitch has your input connected to your out. Remove all power and test to confirm. Try no to move the pedal too much. Turning it upside down might move that lose piece of metal and fix it.
Thanks for the help! I did forget to mention--I've just been testing this on my bare bones test box, just a 1590b with in/out jacks, a dc jack, and alligator clip connections for board in and out, power and ground. It doesn't have a footswitch.
This is the first time I've tested a PNP circuit with it, or a battery powered one. I wonder if I've hooked it up wrong? On the Supa Fuzz board, I have the black battery lead going into the -9v connection. The red battery lead is dangling free--when I tested, I used another alligator clip to connect it to the positive ground wires coming off the board and the volume pot. The power and ground clips on my test box aren't connected to anything. Let me know if this is somehow allowing the in/out tips to just connect to each other.
Well, I was able to get this working again. I did the test you mentioned and a couple of others. Long story short, what I was trying to do with the battery power wiring definitely was the problem. I just went back to the ol' wall wart power, this time with a 100r resistor in series with the -9v input. It does help it work better with the PNP circuit. Thanks again for the help!
That 100R uses the capacitance of the circuit to create a rc lowpass filter on the power supply. I use it on pnp germanium fuzz when i want a good noise floor. It also helps to put your power supply cap after the 100r.
