I built a fuzz face from this schematic: http://www.generalguitargadgets.com/pdf/ggg_ff5_sc_npn.pdf?phpMyAdmin=78482479fd7e7fc3768044a841b3e85a
Initially things were going well, the pedal sounded solid for about a week. After this, I began trying different transistors to see what sounded good. That's when the volume became volatile.
For example: I turn on the amp, test the guitar and it would be very loud when clean. Engage the pedal and there is a huge volume drop (perhaps a tenth the sound output, this did not occur before). Typically that's all, but occasionally there will be jump in volume that rises until I shut the amp off.
I am new to building pedals, but I have plenty guitar experience and plenty EE experience, if anyone has thoughts about what might be going wrong I would be tremendously appreciative.
sounds like a intermittent problem..are the transistors socketed? you could try the wiggle test to look for a solder joint going cold..I have had sockets going loose also ...especially if you swap parts a lot
first thing to do is check the transistor voltages when the volume is good and when there's a drop and compare. if you can't get "good" vol anymore, at least take all voltages and compare em to what they should be (~4.5v on Q2C, etc...)
basically, you want to know if it's the circuit or offboard
that being said, i've had that exact same problem with cheap jacks...a poor connection will do exactly that
Thank you to both of you who replied, I set aside two hours since I posted and waged war against this circuit.
I went about it in the most unscientific manner and changed all the variables at once: several of the wires going into/out of the jacks were somewhat frayed from some earlier problem solving on the board when I took it in and out a few times, I reskinned/resoldered them; resoldered nearly all the board connections; my transistors are in sockets, so I bent the transistor out and ensured good connections to all leads (ohm-meter); I found what believe was the root cause late in the campaign when I stumbled across two wires going into the volume pot which had apparently had their sheaths melt a bit (in a very inconspicuous way-picture two hands intertwined) due to some highly amateur soldering from me, effectively shorting the volume pot entirely if the pedal was jiggled in the right way.