Chalumeau Issues

[bretvh]

So I bought this board a long time ago and finally got around to building it. Having an issue with extremely low output. I can barely hear the modulation effects, and the guitar is indeed distorted, but super quiet. Volume knob doesn't really have any effect on the loudness.

Here is everything I have tried:

- Swapped the PT2399 and LM386 chips a few times
- Verified the PT2399 and LM386 are getting proper voltages
- Cleaned up and reflowed all joints
- Checked resistor and cap values
- Checked wiring
- Checked for solder bridges
- Traced the circuit with a test probe
- The LED does react to the guitar input and the tracking knob does have an effect on it

What I have found is that the sound level is dropping somewhere between R2 and R7/8. I barely get any tone going into the PT2399 on pin 16. If I jumper across from R2 to R7, I get full volume.

The only thing between those Resistors is a trace. Nothing looks damaged on the PCB.

So, this leads me to think that maybe something else later or earlier in the circuit has an issue. I've added a few photos. It looks a little messy because I reflowed everything and scraped gently between the solder pads to ensure no bridges were afoot.

Note that R3 and R9 were replaced with the proper values (I think I somehow managed to put 75k in those spots. I don't even know how...). The other ones look correct to me, but I am also not even close to being adept at deciphering color codes on these things.

Does anyone have any ideas on this one? I thought, "Oh, this will be an easy build!" I mean, I'm not a total newb and I just built two General Tso's compressors over the weekend, which worked first try! Unfortunately, this one has me stumped and I am sure there is something simple I am overlooking.

Thanks in advance for any help!

 

[Big Monk]

So I bought this board a long time ago and finally got around to building it. Having an issue with extremely low output. I can barely hear the modulation effects, and the guitar is indeed distorted, but super quiet. Volume knob doesn't really have any effect on the loudness.

Here is everything I have tried:

- Swapped the PT2399 and LM386 chips a few times
- Verified the PT2399 and LM386 are getting proper voltages
- Cleaned up and reflowed all joints
- Checked resistor and cap values
- Checked wiring
- Checked for solder bridges
- Traced the circuit with a test probe
- The LED does react to the guitar input and the tracking knob does have an effect on it

What I have found is that the sound level is dropping somewhere between R2 and R7/8. I barely get any tone going into the PT2399 on pin 16. If I jumper across from R2 to R7, I get full volume.

The only thing between those Resistors is a trace. Nothing looks damaged on the PCB.

So, this leads me to think that maybe something else later or earlier in the circuit has an issue. I've added a few photos. It looks a little messy because I reflowed everything and scraped gently between the solder pads to ensure no bridges were afoot.

Note that R3 and R9 were replaced with the proper values (I think I somehow managed to put 75k in those spots. I don't even know how...). The other ones look correct to me, but I am also not even close to being adept at deciphering color codes on these things.

Does anyone have any ideas on this one? I thought, "Oh, this will be an easy build!" I mean, I'm not a total newb and I just built two General Tso's compressors over the weekend, which worked first try! Unfortunately, this one has me stumped and I am sure there is something simple I am overlooking.

Thanks in advance for any help!

I’d reflow some of the solder joints. Some of them look a little “globby” and you may have some cold joints or poor “wetting” of the pad underneath.

 

[bretvh]

@Big Monk:

I’d reflow some of the solder joints. Some of them look a little “globby” and you may have some cold joints or poor “wetting” of the pad underneath.

Thanks! I will do that again. They actually looked better before I "reflowed" them last night and took this photo. I guess that's what I get for rushing. I will get them cleaned up and see if that helps. Barring that, any other ideas?

 

[bretvh]

Alright, reflowed everything today and still not getting the expected output/effect. I have tried metering from R2 to R7, and it shows no resistance, but if I try it with the continuity setting, nothing. I understand I am testing a circuit with components in, so a continuity check may not work as desired. Anyhow, if I jumper across those two points, I get more output. Not sure if anyone has any further suggestions, or if this needs to go into the fail bin for now. Thanks!

 

[bowanderror]

I would use an audio probe to track the signal starting at your input jack. If it drops of before the PT2399 inputs, thats where your problem is.

 

[bretvh]

For what it's worth, I ended up just jumpering the two resistors and it works fine. Either the PCB had a defect or I damaged the traces somewhere along the line. Thanks for the help, either way!