How to get rid of this high pitch oscillation in a fuzz face?

[henryd]

Hey guys, I built a silicon fuzz face with nos components on a pigeon fx pcb trying to replicate it as close as possible to an original. I got it to work but there is this high pitch sizzle when all controls are on max. I breadboarded the exact circuit out with similar nos components, and there is no high pitch noise on that at all. I did swap out the tfk bc108c transistors for others on the pigeon pcb but it didn't change it. Is there something that I'm missing? all of the resistors look to be close enough values on my multimeter.

The first half is the pigeon pcb with the noise and second half is the breadboard which sounds find:
Link to soundcloud

 

[henryd]

Does manipulating wires when all hooked up in the enclosure mitigate the noise?

Unfortunately when I move the wires around it doesn't change anything. Was just without the dpdt that I was able to remove and reintroduce the noise with moving that one wire around.

 

[henryd]

How actually old are those NOS eCaps? Have you measured/tested their actual values?
All electrolytic capacitors tend to dry out over time and drift from their original intended values.
Might be worth a look.

I don't know exactly but my guess would be the 80s. Unfortunately my multimeter doesn't have a capacitance meter on it so I don't know, but I'm looking to get one with it soon. They do work completely fine without the dpdt in the circuit, but they could still be affecting it some how.

 

[Big Monk]

I don't know exactly but my guess would be the 80s. Unfortunately my multimeter doesn't have a capacitance meter on it so I don't know, but I'm looking to get one with it soon. They do work completely fine without the dpdt in the circuit, but they could still be affecting it some how.

Have you tried another switch?

 

[music6000]

I got another update. So I detached the pcb from the circuit and connected it to the jacks and pots without the dpdt. I unplugged and plugged back in all of the wires one at a time with none of them recreating this buzzy high pitch oscillation except for one. The wire that connects the negative side of the 22uf cap to the dpdt was making the exact same noise when it wasn't seated properly in the breadboard. But when I put it in well it fixed the problem.

I then attached the pcb back to the circuit, trying to make sure that wire was connected properly but it still made the noise again. So would this mean that the dpdt is faulty or that my wires are not connecting well? When I use a continuity test on my multimeter it says they're all connected.

Have you tried spraying Contact Cleaner down the shaft of the Carling Footswitch while clicking it on & off.
You may have a faulty contact., I had one in a Klon do similiar to what your describing but it was more like static noise while playing!

 

[henryd]

Have you tried another switch?

Yeah originally I had a 3pdt in it and had the same problem. I just can't believe I still can't get rid of this problem, I've tried everything and yet it still persists. Such a weird problem.

 

[Big Monk]

Yeah originally I had a 3pdt in it and had the same problem. I just can't believe I still can't get rid of this problem, I've tried everything and yet it still persists. Such a weird problem.

Try wiring it up in the enclosure but make a point to separate all the wires far apart from one another.

 

[HamishR]

Sometimes it can simply be the layout. Sounds like a different board may fix the issue.

 

[Big Monk]

Sometimes it can simply be the layout. Sounds like a different board may fix the issue.

Looks like the major difference between the vintage board and the Pigeon FX board is:



One way to test this would be to set the breadboard up just like the PCB and see if the noise persists with components and wires in the same proximity as the circuit board.


EDIT: Correction - It looks like you have the iss2 NPN Silicon board, which would not match the iss1 board I show below it. That's my bad.

I have to say that in light of that, board error seems unlikely, although Fuzz Faces are super noisy without deliberate mitigation. Wish I could help more.

 

[henryd]

Looks like the major difference between the vintage board and the Pigeon FX board is:

View attachment 62401

One way to test this would be to set the breadboard up just like the PCB and see if the noise persists with components and wires in the same proximity as the circuit board.


EDIT: Correction - It looks like you have the iss2 NPN Silicon board, which would not match the iss1 board I show below it. That's my bad.

I have to say that in light of that, board error seems unlikely, although Fuzz Faces are super noisy without deliberate mitigation. Wish I could help more.

I really appreciate all your help with this fuzz face. I still have other components for other fuzz faces, so I ordered two more pcb's and am going to build a second with different parts to see if this one just happens to be a combination of old components or the board. If that doesn't fix it then it must just be the wires not blocking noise or bad solder joints. I'll get it to work soon enough!

 

[cdwillis]

If the transistors have a lot of gain you can put a small (47 ohm or 100 ohm) resistor between ground and the electrolytic cap hooked to the fuzz control to stop the oscillation.

 

[Big Monk]

If the transistors have a lot of gain you can put a small (47 ohm or 100 ohm) resistor between ground and the electrolytic cap hooked to the fuzz control to stop the oscillation.

Great point but he’s stated that all the same components and same pots on the breadboard does not have the same oscillation.

(Side note: 47-100 ohm might be too much to start with. Something between 10-33 ohm should do the trick.)

 

[analogdevice]

It's worth noting that breadboards have a stray capacitance between rows which can make tracking down oscillations in fuzz circuits unreliable. It sounds like the common high frequency oscillation issue that occurs when using transistors with too much gain in the stock circuit. I would try the cap from collector to base as mentioned earlier or seek out some lower gain transistors.