SOLVED Curds and Whey - Gettin' wonky in the box

[keevohn]

Hello! Just finished a Curds and Whey today that sounds awesome... but only outside of the enclosure. Once it's boxed up, it starts behaving erratically. Any or all of the following symptoms have occurred:

- Sometimes the Blend pot only has full volume at the extremes and is very quiet for the rest of the sweep.
- Sometimes the Contour switch only has full volume in one position.
- Sometimes everything works as expected, but then drops volume when the knobs are turned.

Clicking the pedal off and on again sometimes changes the symptoms, sometimes not.

Again, everything works just fine outside of the enclosure. As soon as one of the jacks makes a ground connection with the enclosure, the erratic behavior returns.

I'm wondering if this is some type of grounding issue? I built the board bone stock, with the exception of the PPCB adjustable brightness LED breakout board. The CLR and LED pads on the main board were jumpered.

I'm at a loss for where to go from here. Any suggestions are greatly appreciated!

 

[Robert]

Are any of the pot lugs touching the metal body of the toggle switches?

This usually isn't a problem when the toggles are oriented vertically like they are in this layout, but if the circuit is only misbehaving when the jacks are installed in the enclosure that's a pretty good sign that something is making contact with the enclosure where it shouldn't.

Maybe one of the star washers is making contact with one of the pot lugs directly above it? Try it in the enclosure without the star washers, or try insulating the pot lugs.

 

[Gordo]

It might just be the photo but are any of those pots cracked where the boards meet the body? Might have been over stressed with the dust caps on the back and cracked? When you cinch them down they might be getting flakey/intermittent traces? Try flexing them out of the chassis and see if you can reproduce it.

 

[keevohn]

Thanks for the ideas Robert and Gordo. I forgot to mention that the pedal works in the box, but only if the jacks aren't making contact with the chassis - see attached. The pots are in good working order, verified with my DMM.

 

[Robert]

but only if the jacks aren't making contact with the chassis - see attached.

Yep, this points to something making contact with the enclosure.

Try it without the star washers on the toggle switches, or put something between the lugs and toggle switches to insulate them.

 

[music6000]

Thanks for the ideas Robert and Gordo. I forgot to mention that the pedal works in the box, but only if the jacks aren't making contact with the chassis - see attached. The pots are in good working order, verified with my DMM.

Is there clearance between the Power wiire & bent Ground wire on the Power jack when it's in the enclosure, looks like bare wires exposed?
One rule of thumb is Solder the PCB to the Toggle switches & Pots tightened in the enclosure, this is to not put stress on the PCB or bend it.

 

[Giorfida]

Is it happening when just in the enclosure, or only after certain pots/jacks tightened. Try with it out and LIGHTLY pressing the board with a chopstick. I found I had a cracked trace that would only show when tightened that way

 

[keevohn]

Thanks everyone. I'll try each of these suggestions tomorrow and report back.

 

[keevohn]

I tried it without the star washers on the toggle switches per Robert's suggestion, but no bueno. Checked clearance between the pot legs and switches, looked for overlapping bare wires, checked for cracked traces...nothing.

I did notice that the solder joints here seemed a bit dodgy, and possibly had a tiny bridge:


Cleaned that up, re-flowed the ground connections on the jacks, and flushed the pots with Deoxit for good measure. It occurred to me that I used steel wool to clean the legs prior to install, so maybe some worked it's way inside?

Anyway, boxed everything back up and all is working as it should. I don't know what the fix was, but it's fixed, so I'm happy. Thanks again for all the suggestions!