SOLVED Bearfoot Sparkling Yellow OD V2 - oscillations

[Kris100]

HI All, I finished building the Bearfoot SYOD V2 on stripboard (4 knob version) and when I set "M" control fully counter clockwise the pedal starts to oscillate at high frequencies. Following all threads I found others struggling with the same issue with no specific solution.

It seems the M can sometimes bleedthrough between gain stages. I grounded the M pot to the ground strip on the board, just next of the link in column 9. I did my best to run the wires relatively short, input and output jacks are connected to 3pdt with shielded wire. I tried adding a 1k resistor directly to lug 3 of the M pot hoping this would help at extreme (CCW) setting but to no avail. Any ideas what could be done here? Looking at the photo, M3 connections runs alongside right side of the enclosure, M1 runs under the board alongside left side of the enclosure.

Chat GPT recommends to add a 100pf cap between lug 3 and ground to shunt RF noise at extreme setting, I have not tried that yet.

 

[Kris100]

I managed to fix this - by upping the value of the 100pf between pins 1 and 8 of the IC to 220pf the oscillation went down a bit and appeared only when the M pot was fully CCW thus shorting lug 1 to 2 which went to ground. I added a 1k trimmer between lug 2 and ground and tweaked it to just before the oscillations start at M being fully CCW and the pedal works great now. I could replace the trimmer with a fixed resistor now (I think a resistor around 200-300Ohms would be good, would need to measure the trimmer after desoldering to know exact value where I left it. The M pot sweep seems to be fully functionable as is the overall tone of the drive. I also replaced Treble pot with A50k, seems to offer a bit better control over treble as well. Hope this might help someone in the future.