Tone Bender Mk II (Deimos) - Feedback / Squeal Issue

[wbgarman]

The Tone Bender Mk II (Deimos) i just built has an issue where the pedal will create an unpleasant feedback / squeal when the 'Fuzz' (Attack) is turned past 12 o'clock (even with the volume pot on the guitar is rolled all the way off). Below is a video showing the issue:

https://photos.app.goo.gl/mN9dDMReF2APszUo2

Any advice on troubleshooting this issue?

[GGBB]

Tie that to an expression pedal and sell it as a feature.

Seriously though, check your wiring - make sure the input, output and pot wiring is well away from each other and from circuitry. Using shielded wire for the input can help.

[wbgarman]

Tie that to an expression pedal and sell it as a feature.

Haha , that's one way of turning a lemon into lemonade!

I inspected the wiring and I haven't picked up on anything that looks out of the ordinary (see attached image). I am a bit suspicious of the .1 mf. capacitor I placed in C3. I didn't have a film cap available when building, so I'm going to pick one up and see if that helps with the issue.



On a separate note, what is the correct way to bias the the transistors? Should the 'Fuzz' and 'Volume' pots be turned all the way ON or OFF when biasing (I get different readings at different pot positions)?

[GGBB]

The PCB IN wire looks very close to the OUT JACK wire - make sure your ins and outs are as far apart as possible.

I get different readings at different pot positions

That doesn't seem right - but I'm not an expert. Both pots should affect AC signal only, not DC.

[wbgarman]

Quick update to this issue for others who may be building a Tone Bender MkII with the Aion Deimos PCB in the future. While searching the forums, I came across the thread below which suggested a 47uf cap on C8 would resolve the squeal issue. This modification fixed the issue for my build as well!

http://www.diystompboxes.com/smfforum/index.php?topic=118203