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Dirtbaby build problem (no wet signal)

Started by Chris _92, October 21, 2023, 06:04:20 PM

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Chris _92

This is my first post, english is not my first language so i'll try to do my best effort!😅💪🏼

I bought a dirtbaby pcb (2016 ver.) some years ago but I've never built it until some days ago, and I'm getting trouble to get it work. When pedal is engaged, I only hear clean signal, all IC voltages seems OK, I tried with audio probe following the signal path and I think the problem maybe is in IC 2 or IC4, in IC2 I checked with the probe and I get dry signal (no delay) on pin 15 and a noisy low volume signal on pin 14 (Wich I think is the IC output because it goes to IC4), and I get no signal on IC4 input. I tried changing IC2 and IC4 and problem continues.
The only pot it seems to work is the level pot, the others don't affect the signal at all.
Seems like everything is fine but IC2 is not "delaying" I think, but I don't know what causes it. I removed some capacitors around IC2 but everything was fine.

I hope everyone could give me a hand with this, thanks in advance and any suggestion is welcome! 🙏🏼


PIn14 of IC2 is the delay output. But considering your audio signal is low volume, I would double check all those resistor and cap values around IC2. If you have a list of voltages of IC2, that would be helpful.

If you have output on pin14 then you should definitely have input on pin3 of IC4, too. So, somewhere inbetween those two your signal is getting lost. I would try audio probing on each resistor - R19, R21, R22.

Chris _92

Hi Brian! Thanks for your answer, here's what I've got:

IC2 voltages

Pin1- 5.02V.        Pin9- 2.51V.
Pin2- 2.51V.        Pin10- 2.51V.
Pin3- 0V.              Pin11- 2.51V.
Pin4- 0V.              Pin12- 2.54V.
Pin5- 2.8V.           Pin13- 2.51V.
Pin6- 2.44V.         Pin14- 2.48V.
Pin7- 1.14V.         Pin15- 2.51V.
Pin8- 0.85V.         Pin16- 2.51V.

Audio probing Pin 14 I get a low volume, distorted signal, but paying attention I noticed that it's in effect the delayed signal, because it sounds a few milliseconds after I play the guitar, the DELAY pot seems to control the delay time as well.
In R19 I get no sound, neither in the input of IC4.

I guess I'll keep checking values around IC2.

Update: after checking all components around IC2, I've found everything was ok, all values were right, here's a photo of the schematic with a little blue tick on the components I've checked the values

I really don't know what the problem could be.


Your voltages look good. Maybe D2 is causing a problem here with the low delay output. If the signal out of the PT2399 is really, really low, maybe that's why you are losing it before IC4.

Can you remove D2 without too much trouble?

Chris _92

I've already removed D2 but no change. Could it be that the IC4 circuit is generating problems in IC2? reading about the PT2399 it turns out that Pin6 is the one that controls the delay, maybe if I remove R37 I can isolate that part of the circuit and see if it affects the output of IC2