Feedback on Add-verb-v.15

[Anonymous]

Hi,

I just finished my first pedal and it’s getting stuck in feedback loops even on lower level settings.
list of things I’ve checked so far to address the issue:
-The audio and power cables don’t run parallel.

-The ground cables are connected to the pcb and case (checked with a DMM)

-the resistors are all the correct values.

Is there anything else you would advice I check to address this issue?

 

Thanks!

[Billy]

What are you powering it with and what voltages are you getting to the BTDR 3H pins

It’s a good idea to post some nice clear images of the board so that all component values and orientation can be clearly seen and offboard wiring traced

It’s very easy to miss something I know I’ve missed incorrect values etc even after checking numerous times

[Anonymous]

I’m powering it with a 9V adapter.

Here are the readings I got on the pins:

1. 5v
2. N/A
3. .4v
4. N/A
5. .1v
6. .05v
7. 2.4v
8. 2.5v
9. 5.39v
10. 2.5v

[Billy]

Your input and output voltages on the brick pins 3,5 and 6 look very low to me

I’m taking it you get 0v on pins 2 and 4 ground  as it should be

Incorrect voltage can be a cause of oscillation

What voltage do you get on IC1 pins 1, 3 and 5

If the voltage is low particularly on pins 3 and 5 check the voltage at the voltage divider junction where R11 and 12 are joined which should be VB around half input voltage

All your component values and orientation look correct It’s difficult to make out R3 clearly but as far as I can tell its 200K red black black orange brown the orange band just doesn’t look as bright as it usually is because of the reflection I think

[Barry]

I suggest a complete re-flow of the board and a clean up of the off-board wiring as well.

The solder needs to flow into the solder pads. Not excessive but you will have cold solder joints if it is only sitting on top of the pads. So use your iron and reheat all of your solder joints and add a little extra solder while doing it.

Cold solder joints will affect your voltages and keep your project from working.

Here are some photos of my concerns:

 

In this image note in particular the Brick solder pads.

 

This image note in particular the POT solder pads, especially the DECAY pads.

 

In this image your ground wire is touching your +9v pad.

Ideally you should push the wire through and solder from the back so that your pvc is flush with the PCB.

 

 

[Anonymous]

Interesting, I’m getting 4.53v on all 3 IC1 pins and also on the voltage divider.

[Anonymous]

Also, thanks for the soldering tips, Barry!

[Billy]

Once it’s working if you can post all voltages for anyone else that may run into this type of problem it’s always good to have working voltages

Well spotted Barry I never even noticed those joints I was too busy checking component values etc a few do look as if the solders not fully melted onto the pads so hopefully that’s it

[Anonymous]

Will do! Thanks for your help! I had to order a new soldering tip cause the “sharper” tip accidentally got some microfiber cloth melted on it (Hence why I used a larger one which ended up being difficult to get more precise soldering towards the end of my project.) So it might take a sec for me to be able to try this fix out, but I’ll keep you guys posted. Hopefully cleaning up the solder will fix the issue.

[Author]

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