1-knob Fuzz Bonanza PCB not working, HELP MUCH APPRECIATED

[danejo]

I designed and ordered a pcb that uses DIP switches to change values between 3 fuzz pedals included in the 1-knob fuzz bonanza layout. Sound is coming through but there are some issues:

1. There is a large volume drop, the tone is very dark/bassy and no sound goes through if I turn up the pot too much
2. There is a whining sound when the switch is set to "true bypass" (this I do not understand how?)
3. If I touch the metal case of the transistor to the right as well as the pot casing with my fingers the correct tone comes up but there is a lot of squealing sounds.

I have replaced the switch and the trannies and the problems are exactly the same. Are there any general things to look out for with these symptoms? I feel confident my board design is accurate yet I am increasingly doubting it. All the joints look fine and there doesn't seem to be any shorts.

Any help I can get would be GREATLY appreciated.

[IvIark]

There's something wrong with the layout. You have the Q2 emitters connecting to the other side of the output cap dip switches and so directly to the output going to Volume 3.  The Q2 emitters should only be connected to either the 120K or 150K resistor to Q1 base, the 1K resistor to ground and the 10u cap to ground.

Did you miss the cut under the 820 ohm resistor?

[IvIark]

Or is that another layer right over the top?  It's hard to tell sometimes following a layout with more than one layer.

[danejo]

Dude you're my hero! I did miss that cut under the 820 ohm. I cut out the emmiter and 10uF node, linked them together and presto. Sounds great and it is really fun seeing the difference that the resistor and cap values make.

I am forever in your debt. Let me know if you ever need anything (physics/calc tutoring, pcb designs, love letters, etc.) You sir have made my day.

[IvIark]

Excellent, glad you sorted it out, especially after the trouble you've gone to getting the board done and with the build.  

It's a nice idea this, and even more versatile than the 3 pedals individually because you can have caps and resistors in parallel with each other giving even more potential values.  This would definitely be a good tool for someone who wanted to know what each of the components in a Fuzz Face type circuit did, to see what audible difference each component makes.

For even more versatility consider swapping the 1K resistor for a 2K2 trimmer or even an external pot.  Then you can alter the gain too.

[danejo]

I'll definitely add in a 2k2 trimmer. Thanks again.