I've built a GE PNP fuzz pedal following the scematics on the site. I've used the proper AC128 transistors but there have been some problems...
The fuzz sound works, but the signal coming out of the amp is rather weak. I have to turn the volume right up on the amp before the the fuzz sound is audiable. Annoying when you switch the fuzz pedal off and the volume jumps right up. Also the pedal does that popping thing when you switch it on and off, I've put a 1mega ohm resistor to ground just before the 2.2 uF capacitor but it still makes that noise. Finally the "fuzz" control doesn't seem to change anything.
I've given anything a check through and it I don't know what i've done wrong. I'm using a 3pdt foot switch so that I can have an LED indicator...
...I'm using a 22k volume pot instead of the 100k pot as I don't have any lying around at home, but i don't see how that should really effect things.
The popping when you switch it on and off could be caused by a leaky input or output capacitor, or if the input capacitor (which is polarized) is turned around the wrong way. For a PNP circuit, make sure that the positive lead of the input capacitor is turned away from the base of Q1.
The fuzz control not doing anything could be caused by Q2 being saturated by too much voltage on the collector. Take a voltage reading on the collector of Q2 and see if it's in the 4.5V - 5V range. If it's not, you can use a 20K or 25k trimpot to dial it in perfectly. The voltage on the collector of Q1 should then fall into the 1V - 1.3V (or so) range. Also make sure that the 3rd lug of the fuzz pot is connected to the emitter of Q2, that the wiper of the pot has the 20uF or 22uF capacitor to ground (and that it's turned around the right way since it's also polarized), and that the 1st lug of the pot is solidly grounded.
Thanks, I've managed to stop the poping sound (I put a diode to stop the acidently reversing the battery on the clip thing, to protect transistors) I took that out and the popping now stops when you turn it off and on.
The voltage on the collector of Q2 is now arround 5.5V after I put a 22k resistor in series of that leg. on Q1, the collector is about 0.01 volts and the base is 0.02 volts. I don't know what's going on there...
...I've checked everything else and it seems to be wired correctly with the capacitors the correct way round.
