My fuzz face experience, debugging

[usbdevice]

Hey all, just wanted to share an experience I had tonight.
I'm a newbie on this forum and to electronics as well. I've been reading here for quite a while now but haven't really posted yet.
I've built a couple of things over the last year or so and this place is a great resource. Big thanks out to everyone who posts here.
OK, now on with the story.

I've had a fuzz face on my breadboard for a week or so, trying out different input/output caps and transistors. I'm using a schematic found on GGG - npn, negative ground, silicon transistors. Last night I figured it was time to solder the thing up and put it into a box. Since the box already had 3 holes drilled for pots I decided to implement an input cap blend control (tried it out on the breadboard first). After I was satisfied with the sound I perfboarded it and went on to put everything into the box.
I hooked it up and... you guessed it, no sound, no wait just a faint idea of a fuzz when I hit the strings hard with the gain and volume controls al the way up. Sounded like the bias was off somewhere. So I open up the box and start probing with my dmm. Everything looks normal except for q2's collector which was just 20mV away from the supply voltage. I went over the circuit 20 times looking for solder bridges, bad solder joints and layout mistakes, checking all the off-board wiring and trying some other transistors. Couldn't find anything wrong so I decided to probe around with an audio probe (had to build it first). Signal was good at the collector of q1, and of course still wrong at the collector of q2. I should note that first thing I did was to remove my only "real" mod, the input cap blend even though it worked perfectly on the breadboard, just to be sure.
After 2 hours of going over it again and again I finally found the error in the 1 place I hadn't bothered to look before, and I only noticed it by accident: the pots (I did check the wiring, but not the pots themselves). Turns out I accidentally swapped the gain and volume pots when I put everything into the box. That's right, 1k volume pot, 500k gain pot, duh!
I guess I learned something today, you can't be lucky all the time, especially not since I usually start building these things way past midnight. All my previous builds had worked right away, a ross distortion, 2 bazz fusses, a sonic distortion, a triple fuzz and a phozer, and I had started to take things for granted, bad bad boy.

Anyway, the thing is working and I really like the sound. I might even try one with germaniums in the future, I understand they sound quite different.

thanks for listening
lenny

[MartyB]

Cool Lenny!   Welcome to Aron's forum.  Glad you got it working.  You might try using different color wire.  That sometimes helps me keep offboard components straight.
MartyB

[jmusser]

It takes perseverance on these things. I know I have done that one there, along with, leaving the transistors out of the sockets, not having the battery hooked up, putting the ower and ground rails together, wiring a chip socket backwards (pin 1 for pin , etc. The main thing is to dig in there and find the problem. At least 80% of the time, it's something simple, and something that is sooooo simple that you assume it couldn't possibly be the problem! A lot of times I post my goofs, just so other people won't make the same mistakes, and they'll have one more thing to look for while debugging. Glad it all worked out for you, and welcome!

[Pedal love]

Great detective work, Lenny. When I diy ff's and get an output of good fuzz, but barely detectable volume, I have to remind myself about the pots. Not only have I swapped pot positions, but I tend to use a lot of bad pots for projects, so I have started going there instantly. Very cool. pl