Shula Fuzz

Crash102

Well-known member
Hi all, thought id post here as I’m getting near the end of things I can check and I’m to the point of going though every single resistor to check if that’s where the issue it

The pedal works (ish) , the led works, it even passes a fuzz sound.

However, the signal works best with the low notes and only if I dig in to them. Higher notes seem to die right away.

I’ve switched out the footswitch, the jacks, the transistors,

I’ve scrubbed the board clean

I’ve gone back and reflowed every joint.

I even tried de-ox it on the pots

I suspect it’s either a wrong resistor or maybe a faulty pot,

Just thought I’d crowd source it, as I this seems like it should be one of the easier ones to build. F2226BC3-C0CF-4C90-A27B-EC8C5DB392DC.jpeg E63E2BF1-0498-488A-868C-54031A458C53.jpeg 99C579CE-962F-42DF-853F-A3BAF345EB3E.jpeg
 
Solution
Sounds like a mis biased transistor if you're having to dig in to get sound

Your pictures out of focus so can't really see your resistor colour bands clearly

Check values of transistor biasing resistors on each transistor collector, base, emitter

I can't see for certain but R13 and 15 look to be the same R13 should be 8K2 and R15 82K they both look 8K2 but as I say can't really make the colour bands out
Maybe time for an audio probe and trace the signal through the circuit until you find where it's going sub-optimal.

I'd pay particular attention while doing so around the melted caps, as that might be where the problem lies.
However, I've melted caps far worse and still had my pedal work.

Magnifying glass and inspect for a micro bridge, especially under the sockets.
Check the diode glass for cracks.
Like you said, check each and every one of those resistors' colour-bands...
 
Maybe time for an audio probe and trace the signal through the circuit until you find where it's going sub-optimal.

I'd pay particular attention while doing so around the melted caps, as that might be where the problem lies.
However, I've melted caps far worse and still had my pedal work.

Magnifying glass and inspect for a micro bridge, especially under the sockets.
Check the diode glass for cracks.
Like you said, check each and every one of those resistors' colour-bands...
When I took the pictures I noticed the burnt cap, but I had to have done it while reflowing everything so I know that’s not the cause.

I didn’t even think about diode class cracks.

Here’s to hoping I find it before replacing every single part in this quest.
 
It's probing time...

Kf9WnfT.gif
 
Is this the PPCB Shika Fuzz? What transistors did you use? Did you make any substitutions?
It kinda sounds like the trannies might be installed backwards. They're not if those are legit 2N3904's but if you subbed something else then the pinouts might be different. I'd check the pinouts on what you have. Do you have a transistor tester?
 
It is the Shika. I’ve thought it was it might be early in my trouble shooting process a as well. I’ve changed and substituted the 2n3904’s. And tried them facing both directions. Didn’t make a difference
 
Sounds like a mis biased transistor if you're having to dig in to get sound

Your pictures out of focus so can't really see your resistor colour bands clearly

Check values of transistor biasing resistors on each transistor collector, base, emitter

I can't see for certain but R13 and 15 look to be the same R13 should be 8K2 and R15 82K they both look 8K2 but as I say can't really make the colour bands out
 
Solution
Sounds like a mis biased transistor if you're having to dig in to get sound

Your pictures out of focus so can't really see your resistor colour bands clearly

Check values of transistor biasing resistors on each transistor collector, base, emitter

I can't see for certain but R13 and 15 look to be the same R13 should be 8K2 and R15 82K they both look 8K2 but as I say can't really make the colour bands out
Good call, R13 was correct, but i had R15 with 8k2 instead of the 82k.

That fixed 75% of the problem, so then following the logic of that, I removed the sockets and existing transistors, and put new ones in. Also saw that the trace from Q4 to C14 might possilby be suspect so I bridged those,

And while i was at it, replaced the burned capacitor.

and now it's working as it should be.

Thank you.

.
 
Back
Top