Need help, homemade multi effect pedal noise issue

[charmonder]

I was trying to get these 6 different silicon transistor fuzz overdrive pedals all into one box, there's two knobs, input level, output level, then a 6pdt switch to select which circuit gets used. (get it? Its like a line 6 distortion modeler but analog) I tested and had it working perfectly on breadboard, with 9v running through a 100ohm resistor and 47uf cap to ground before it gets to each circuit. now that I have it all soldered up I have a squealing sound in all modes.     Is it my soldering job? Or does that sound like a decoupling issue, I am stumped. 

Thanks for any advice!

[nocentelli]

schematic? Pictures?

[deadastronaut]

shielding on inputs?..

[petey twofinger]

i have had this issue before .

once it was something was touching the chassis

once it was the circuit board "flexed" a bit when it was screwed down becaus ethe holes for the standoffs were not lined up perfect , so i expanded the pcb holes with a drill .

the other was that 2 jacks on the circuit were never intended to be grounded , so when i modded it with metal jacks , it worked till it was in the chassis , at that point it all grounded .

i would suggest removing it to see if it fixes , to make sure , then take it slow from there . start reinstalling it  but checking it as you go , one step at a time , if possible .

good luck .

[Keeb]

I tested and had it working perfectly on breadboard

Did you try the circuits once they were assembled?
What material did you use for the final layout?

If you had it working on breadboard it should just a debugging issue (solder bridge, layout error etc.) so keep at it and this thing will work!

[petemoore]

  Osillation could be...
   a high gain circuit fed by a high gain circuit, a fuzzface can oscillate, a power supply issue...
  Try a clip-wire-probe to ground [or more] to ground the input of high gain circuits which are sitting idle [if not using bypass configuration which already does this].
   To at least determine some proximity of where to shunt or take other measures to reduce or eliminate squealing.

[charmonder]

Ha I caught it! Thanks for input everyone, I love the enthusiasm around these parts. 

Turned it was just one of the fuzz circuits spoiling the whole bunch. I could tell because I put my fingers on it and it changed the oscillation frequency. I cut it out and the 5 others work perfect.

I highly suspect it has something to do with the fact that the sixth fuzz pedal uses a 220uf capacitor( this is just a stupid design I made, I don't think there's any reason it needed to be a 220uf ).   From an electronic standpoint, does that make sense? Was the problem that I exceeded the decoupling capacitance in the circuit?


Of this run of fuzzes the winner so far is the Tim Escobedo punch in the face. The slow attack thing is unreal sounding, I bet it'd go good with envelope filter.

[charmonder]

Turns out changing the size of that one cap didn't help anything, it's past my willingness to save it now. In retrospect Im pretty sure it was only a silicon fuzz face derivative with random have-no-clue-what-I'm-doing changes like 220uf capacitors