SOLVED Delegate Squeal at 3.3mHz

[krakenmeister]

Hey folks, I built myself a delegate and experiencing a 3300hz squeal. This only occurs when the pedal is plugged into power, and it doesn't matter if the pedal is on effect or bypass, the squeal is still there.

Any ideas as to what this squeal might be from? Other than that, the pedal works perfectly. Squeal noticeable lowers /disappears when the tone knob is lowered

 

[krakenmeister]

Any thoughts? I looked at the schematic and the only thing that makes sense to me is that one of the three transistors is bad? But I'm unsure of how to test this theory.

Possible feedback look?

 

[Dan M]

It’s usually not a bad component. Could be, but usually not.

https://forum.pedalpcb.com/threads/...s-when-an-issue-arises-with-a-pcb-build.7081/

 

[krakenmeister]

Been soldering and putting together electronics since 2007.

 

[fig]

That's a lot of experience! Looks nice!
Do you have insulation between those pots and the pcb?

 

[krakenmeister]

@fig they have about 5mm gap between the pots and the PCB

 

[Chuck D. Bones]

Any parts substitutions?
Have you tried a different power source?
Looks like the pot bodies might be touching some of the leads on the adjacent pots. Dust covers are highly recommended.

 

[krakenmeister]

@Chuck - no sub parts to my knowledge, the 1044 IC is a "MAX1044" from maxim if that makes any difference

I tested with 2 different power sources

 

[Chuck D. Bones]

Did you buy the parts as a kit? Not sure I understand what you mean when you say "no sub parts to my knowledge."

 

[krakenmeister]

@Chuck not a kit; sourced everything myself, I just mean I'm not sure if the charge pump is the correct one

Also adding insulation for the pots did not change the output of the 3.3mHz tone

 

[Chuck D. Bones]

IC2 pin 5 does not look like a good solder joint from the component side. It might be OK, but can't see it from the solder side because the SUSTAIN pot is obscuring the view. MAX1044 should work fine, unless it's counterfeit.

 

[krakenmeister]

@Chuck D. Bones appreciate you checking it out, solder is good on the other side

 

[Robert]

I'm not familiar with the different suffixes of the MAX1044, but at least one version has an oscillator frequency of 5kHz.

 

[daeg]

This is such a common problems with Charge Pumps. Remove it and see if the circuit still works.

Then, take a picture of the chip or write down the part number from the face of it, and let us know which supplier you got it from.

 

[krakenmeister]

@daeg thank you I’ll remove it and try and source another one! It’s a MAX1044 (left column from @PedalPCB’s pic)

Thanks for having look folks if it’s a bad charge pump then that’ll be good news. Anyone know where to source them? I got mine from digikey

 

[daeg]

Definitely try the circuit with the charge pump removed. It should work.



My thinking out-loud on this:

• VCC will be about 1/3rd, so you're losing a lot of headroom, but that probably won't be noticeable.
• Q1 is wired as a phase splitter, and will always bias at 1/2 VCC.
• Q2-Q3 should still be able to perform their gating duties.
• D3 will lose a lot of brightness so only lower compression ratios will be available.
• Nothing else will be affected.

 

[krakenmeister]

@daeg you wonderful human being. That worked, the squeal is gone! Again, bought from digikey. I'll try to source a TC1044 instead of the 1044MAX.