Spirit Box white noise - PT2399 problem?

[sticky1138]

My Spirit Box, which had been working just fine for over a week, now puts out white noise/no dry signal both when bypassed and engaged, even though the LED still works. I went through the standard troubleshooting checklist (looked for cold joints, shorts, etc.) and even did a full rewire of the off-board components since I initially thought it was a bad footswitch or jack connection preventing the bypass signal, but no, same problem.

For a couple seconds I was able to get a echo/reverb on the white noise when I touched around the PT2399/transistor area of the PCB, but that didn't last very long and I haven't been able to do it since. I tested the connections of the Belton and all the other ICs and everything is secure, so that leads me to believe it could be a problem with the chip.

I've read that PT2399s can behave questionably. Is it possible my chip just crapped out? If that is the case, would you expect the bypass signal to be white noise?

 

[blackhatboojum]

I can’t say with 100% certainty but, it does sound like you have a faulty chip and that it’s latching up. Even though it’s bypassed it will still do this and give you white noise when that happens with some circuits. Have you tried disconnecting power to to it, waiting a few seconds, and trying the effect again?

 

[Barry]

You probably want to order several PT2399's for builds that use them, put in a socket and swap through and find the best one for that circuit

 

[finebyfine]

Are your tl072s legit? Counterfeit ones really show their true color and add noise in cleaner circuits like the spirit box.

I agree that it’s probably the pt2399 - just haven’t had that exact behavior with one myself.

 

[sticky1138]

Everything is from Tayda, never had a problem with their parts after more than a dozen orders, but I suppose there has to be a dud sometime. I swapped the TL072s with some others without luck. I'll probably order a handful of PT2399s next time, unfortunately I just placed a separate order a few days ago, wish I would have known earlier!

Also, after a few more tests, I wouldn't say it's necessarily generating more white noise beyond regular amp hum, if that means anything.

 

[Robert]

Nothing on the PCB should affect bypass.

I would look closely at the wiring (again), jacks, switch, or even your cables.

If it doesn't pass a clean signal in bypass it's not the TL072s or PT2399 causing the problem. The pedal should pass a clean signal in bypass even with no power applied.

 

[blackhatboojum]

I’m an idiot and retract my comment. I missed the part about “NO dry signal” in your post.

 

[sticky1138]

I'm probably going to end up swapping the 3PDT/breakout board, all the wires and both audio jacks here shortly. I've been messing with it for a while now with it and haven't pinpointed a bad connection yet. It makes sense that it would be an off-board issue since it doesn't have a bypass signal.

 

[fig]

...or throw up some pics. Some of these folks can spot a mole hair on the northbound side of a southbound mosquito at 1000 paces.

 

[sticky1138]

...or throw up some pics. Some of these folks can spot a mole hair on the northbound side of a southbound mosquito at 1000 paces.

Alright, then here's a challenge for all the aspiring entomologists on this board before I face the music (or lack thereof) and rewire a third time:

https://imgur.com/a/JpSTfhl

There is a decent amount of residue now from all the soldering and resoldering, which is why I was thinking about swapping for a fresh 3PDT/breakout board and cleaning that one later. Also confirmed that amp/guitar/cables/power supply are not the culprit.

 

[untamedfrontier]

If you bend the LED leads so they aren't touching the case, does anything change?

 

[sticky1138]

The exposed legs of the LED are normally covered and positioned more neatly, but I moved them for a better view and they aren't touching anything when I test it.

 

[Robert]

Do you have a DMM?

If so, with the pedal bypassed (and no power applied) check for continuity between the tip contacts of your Input / Output jack.
While you're at it, make sure neither of them are shorted to ground.

Then with the pedal "active" (still no power applied) check for continuity between the tip contact of the Input jack and the IN pad of the PCB.
Do the same for the tip contact of the Output jack and the OUT pad of the PCB.

 

[sticky1138]

Just tried it and was able to get continuity with all your suggestions.

 

[blackhatboojum]

Just tried it and was able to get continuity with all your suggestions.

Just to clarify… on the first test @PedalPCB suggested, did you have continuity from the tip contacts to ground? If so, then you have a short and that’s no bueno.

 

[Barry]

Can you get a shot of the other side of the board?

 

[sticky1138]

Just to clarify… on the first test @PedalPCB suggested, did you have continuity from the tip contacts to ground? If so, then you have a short and that’s no bueno.

No connectivity between either tip to ground.

Without the brick:

https://imgur.com/tU5BCJE

 

[blackhatboojum]

No shorts but continuity from input to output … Have you checked your instrument cables? Seriously, that’s the only thing it could be. If you have continuity from input to output but no signal when you plug into it, then you have an issue outside of the pedal.

 

[sticky1138]

No shorts but continuity from input to output … Have you checked your instrument cables? Seriously, that’s the only thing it could be. If you have continuity from input to output but no signal when you plug into it, then you have an issue outside of the pedal.

Ok, embarrassing user error on the last part...I tried again and there must be a short since there is in fact continuity between each tip and ground. I was just being stupid with the DMM. Is there a straightforward way to diagnose whether that is on the PCB or in the wiring?

 

[Jonnytexas]

Did the output jack twist to where the tip connection is touching the enclosure? Also, is there a little solder blob between 2 and 5 on the FS?