ADHD - squeal? Ish?

[Lytt Effects]

Ok, not exactly sure how to describe what’s going on, but basically my most recent build (newest iteration of ADHD w/ enhanced bypass board) is making a high pitched squealing noise. When pedal is in True Bypass mode, the noise only occurs when the pedal is engaged. When the pedal is in Buffered Bypass, the pedal makes noise at a much lower volume when bypassed, and then gets much louder when engaged. In all instances, the guitar comes through. Sounds perfectly normal when in TB, and sounds just fine when engaged, but the noise is very present.

I have not tested voltages anywhere yet, as I don’t know exactly what I’m looking for. I have not combed over resistor values yet, as my brain needs a break from it, so thought I’d bring it here in the meantime. I have tested with two different power supplies, both of which produce the same result, and both are known to be good supplies.

 

[jwin615]

Any change of you pull your in/out wiring away from the pcb?

 

[Lytt Effects]

Any change of you pull your in/out wiring away from the pcb?

Nope, no change. Didn’t get to do much troubleshooting tonight, so I’ll leave it for the morning before work.

Steps thus far:

- swapped power supply
- removed from enclosure and re-tested
- checked for bridges, gave another clean up wipe, brushed off board

Tomorrow, I will try swapping out the TL082, and then I will verify each resistor value. After that, I’ll start reflowing some joints, mainly on the tants, as they seem a bit off to my eye. Then I’ll get the audio probe out and see what’s what.

 

[Lytt Effects]

Voltages: Supply reading 8.81v at power jack, 8.56v at cathode of D100 (reverse polarity protection)

TL082:

• Pin 1: 4.28v
• Pin 2: 4.28v
• Pin 3: 4.08v
• Pin 4: 0.00v
• Pin 5: 4.27v
• Pin 6: 4.28v
• Pin 7: 4.28v
• Pin 8: 8.57v

Q1 (2N7000)

• 1 (S): 4.28v
• 2 (G): 4.28v
• 3 (D): 4.28v

Q2 (2N7000)

• 1 (S): 4.28v
• 2 (G): 4.28v
• 3 (D): 4.28v

Enhanced Bypass Board:

2N5457 (left)

• 1 (D): 7.31v
• 2 (G): 1.17v
• 3 (S): 0v

2N5457 (right)

• 1 (D): 7.31v
• 2 (G): 1.17v
• 3 (S): 0v

2SC1815

• 1 (E): 3.05v
• 2 (C): 5.51v
• 3 (B): 3.51v

I believe I have the pinouts correct for the transistors. I'm reading the pins from left to right, 1-2-3, when looking from the top down. Flat face of the transistor is on the bottom. If that makes sense.

Schematic:

 

[Locrian99]

those jumpers for the diodes are not needed. I dont think they are related to your issue but I would remove them.

In narrowing it down it sounds like whatever the problem is has to be shared with the buffered bypass board and the circuit itself to me. If you can hear it in buffered bypass mode, assuming it is getting amplified by gain of the circuit when activated. Does the volume control effect the level of squeal when its not bypassed?

 

[Locrian99]

This might help at least seeing how the bypass board connects into the circuit

https://docs.pedalpcb.com/project/archived/ADHD.v2.pdf