Karen issue (with video)

[Yalesmith]

Hello. I built a Karen pedal pcb and it’s having an issue with the gain width trim. See video below.

Also, if anyone has any voltages , that would be great!

Thanks

 

[BuddytheReow]

The video is nice, but we need to see pics of your build. Both sides of the board if you can

 

[music6000]

I thought this was going to be a video about a person called ''Karen'' ranting on!
Definately need Pictures.

 

[Yalesmith]

See attached. I think maybe if someone had some voltages that would be great as well. Thanks!!

 

[Locrian99]

Is there a reason you used a 1458 vs 4558?

 

[DailyDovetails]

my guess is this spot on C3. I’m not sure why but it looks different. I’m pretty sure C3 is there to prevent oscillation.


Also I’m not familiar with the 1458.

 

[Locrian99]

Also I’m not familiar with the 1458.

I tend to think since its a dual op amp it shouldnt matter but the nature of the issues makes me wonder.

 

[Locrian99]

Should be real easy audio probe til you find the noise. I suspect its at the op amp and its feedback loop based on the width pot. Re solder double check values. Id try a 72 since im assuming you dont have a 4558

 

[music6000]

Does the trimmer have 205 written on the side?
Definately need to reflow the solder, a lot of those resistors need to look like the one under the Op Amp.

 

[Yalesmith]

Should be real easy audio probe til you find the noise. I suspect its at the op amp and its feedback loop based on the width pot. Re solder double check values. Id try a 72 since im assuming you dont have a 4558

I do have a 4558… the op amp I was using before was the only one that would tame the oscillation.

 

[Yalesmith]

Well I’m partially a dummy…. The pcb is a Kadundra and not the Karen!!! Apologies!! I re flowed the the op-amp. It is definitely an op-amp issue but can’t seem to figure out. I got them mixed up because I just built the Karen.

 

[music6000]

The PedalPCB Kadundra is the Karen???
Can you confirm the trimmer has 205 stamped on the side?
We can't resolve an issue if you don't confirm what we can't see.
Pull the Op Amp out & with the Power unplugged, do a continuity test from pins 1 to 2, 2 to 3, 3 to 4, 5 to 6, 6 to 7 & 7 to 8.
There should be no connection.

 

[Yalesmith]

Definetly stamped with 205 and no opamp continuity

 

[music6000]

You need to reflow the hole PCB, there are a lot of Cold joints as I mentioned above with the resistors pads should be full of solder on the component side!

 

[Yalesmith]

Yep a cold solder. I re-soldered the board and now it works!! I rushed the build and did a poor job soldering

 

[music6000]

Glad you got it sorted out, a thanks of appreciation goes a long way if you wish to get help on here with future builds from the many Members on here that are appreciated for their Help!

 

[Yalesmith]

Thanks!!