Sanguine low output

[lifer2624]

Hey everyone,

I'm running into an issue with my Sanguine build. This is my 14th build, and it's the first time I've had a problem like this. The circuit works, but when the pedal is engaged, the output is attenuated. So the signal is still getting through but the clean signal noticeably louder.

The only obvious issue I've encountered so far is that two potentiometers (mid and treble) broke while buliding, so I desoldered them and replaced them. While removing the mid pot, I suspect the solder pad for leg 1 may have come off, but when I checked for continuity, everything seemed OK.

I can tell that the volume and gain pots, as well as the aggression switch, are functioning properly. I'm not entirely sure about the mid pot, and I’m having a hard time determining whether the treble and bass controls are working as they should.

To troubleshoot, I also swapped out all three op-amp ICs, but that didn't change anything.

Has anyone encountered a similar issue or have any ideas on what to check next?

Thanks!

 

[Robert]

Check for continuity between these points.

(For example, Gain Pot Lug 1 to the Right end of R16, looking at the component side of the PCB)

Gain (1): R16 (R)
Gain (2): C12 (+)

Volume (1): GND
Volume (2): OUT pad
Volume (3): R33 (R)

Treble (1): C20 (R)
Treble (2): R24 (L)
Treble (3): C19 (L)

Mid (1): C25 (R)
Mid (2): R30 (R)
Mid (3): R28 (R)

Bass (1): R22 (R)
Bass (2): R23 (R)
Bass (3): R21 (R)

 

[lifer2624]

Thanks for the quick reply!

All those points check out, but after further testing of the pots, I found that the gain pot seems to be faulty. Measuring the resistance from end to end changes depending on the wiper position.

 

[Robert]

Are you making that measurement with the pot removed, or still in the circuit?

That's normal if the pot is still in circuit.


If all of the continuity measurements checked out then the traces to the pots are fine. Post some pics of the component side of your PCB.

 

[lifer2624]

 

[lifer2624]

While tracing the signal path with an oscilloscope, I’m getting a waveform up to the left side of R17 (top view of the board), but there's no signal present at pin 2 of IC2. The output signal is very low, and the tone and bass potentiometers have no effect on it.

I tried bypassing the trace by running a jumper wire from the left side of R17 to pin 2 of IC2. This restores signal flow, and I see more activity at the output. Additionally, the tone and bass pots begin to function and affect the signal as expected. However, there's still no signal making it to the next gain stage (IC3).

Next, I lifted the right leg of R17 from the board and ran a jumper from that lifted leg to pin 2 of IC2. The result was identical to when the leg was in the board—no signal through IC2 and the tone/bass pots not working

 

[BuddytheReow]

Considering the parts count, it sounds like you've got a bad solder joint somewhere. Can you show pics of the underside of the board? Might be a good idea to reflow suspect joints.

 

[lifer2624]

Hey guys, I'm at a complete standtill here. I have reflown all solder points and no change. I do notice that the signal picks up if I'm touching the back of the board on the caps below the gain knob.

I'm also noticing the signal doesn't seem to be affected by the treble or bass pots. The signal does change from the mid knob but the signal tends to get erratic when my finger are spinning it.

When scoping the circuit I'm seeing it all the way up to the left side of r17 and then it dissappears.

I'm not sure what to think as everything is all new parts and out of 14 builds this is the only one to give me this kind of trouble.

Also don't mind that jumper wire, i was using it for testing purposes to pass the signal around r17 to ic2 pin 2

Any help is appreciated

 

[jimilee]

How do the voltages on the ICs look?

 

[szukalski]

Time for a probing. An audio probing.

 

[lifer2624]

All those voltages on the ICs are measuring as they should be.

And yes lol I have been probing. I lose the signal on the other side of r17 where it meets pin 2 of IC 2. I've switched out r17 for a new one and have the same issue.

 

[jimilee]

All those voltages on the ICs are measuring as they should be.

And yes lol I have been probing. I lose the signal on the other side of r17 where it meets pin 2 of IC 2. I've switched out r17 for a new one and have the same issue.

Remove the IC and see if you have audio at pin 2 of the socket.

 

[lifer2624]

The signal shows up on the socket with the chip removed