[HELP NEEDED] EHX - Ripped Speaker - Sizzling Sound

[CrustyD3mon]

Hi everyone,
I Have here a EHX Ripped Speaker, that are makind too much noise, a kind of sizzling sound.
I was measuring around and inspecting all the components, and i'm having some troubles identifying the cause, in a first place i was thinking it was the R40, a drop down resistance in the circuit, because this resistance was grounding in both sides. I replaced the resistance and its grounded anyways,..than i saw that it's supposed too...

So i started to measuring all the IC components and i have here the voltage in hope you guys can spot something strange that help me to identify the root cause.

For instance, I measured all with the footswitch on and pots to the maximum, and amp and guitar conected closing the circuit:

U1 (OP1678)

1- 4.18v
2- 4.18v
3- 4.18v
4- 0
5- 3.45v
6- 4.17v
7- 4.18v
8- 8.29v

Q3 (2N3904 J16)
C - 6,14v
B - 0,70v
E - 0,07v

Q4 (2N3904 J16)
C - 6,31v
B - 0,70v
E - 0,07v

Q5 (2N3904 J16)
C - 0,58v
B - 1,23v
E - 0,54v

No visual damages on the board, even under the magnifying sup, the electrolitics i already dissolder and checked with multifunction Tester TC-1.
So i need help....

 

[Robert]

https://docs.pedalpcb.com/schematic/Schematic-EHXRippedSpeaker.png

R40 should not be grounded on both sides, one side is the input to the circuit.

It might measure shorted if the pedal is in bypass or the input jack is the shorting type and nothing is plugged in.

 

[CrustyD3mon]

https://docs.pedalpcb.com/schematic/Schematic-EHXRippedSpeaker.png

R40 should not be grounded on both sides, one side is the input to the circuit.

It might measure shorted if the pedal is in bypass or the input jack is the shorting type and nothing is plugged in.

Ok, now i understand. I was testing the resistor without input jack, with input jack its not measuring shorted. So that at least its working normal...

 

[CrustyD3mon]

https://docs.pedalpcb.com/schematic/Schematic-EHXRippedSpeaker.png

R40 should not be grounded on both sides, one side is the input to the circuit.

It might measure shorted if the pedal is in bypass or the input jack is the shorting type and nothing is plugged in.

If it was you what you recomend to test next?

 

[Robert]

Aside from the noise, does the pedal seem to work?

Your best bet would be to use an audio probe or oscilloscope and determine where the noise is introduced into the signal path.

 

[CrustyD3mon]

Yes, everything works aside from the noise, i made myself an audio probe, but i need someone to guide me in terms of what points should i test.. something like, test this capacitor...test this transistor this way ...and so on...i don't have too much experience with it....

Also, you gave me the schematics but its labeled different because i think you gave me the schematics of the paper scratch, right?

 

[Robert]

Also, you gave me the schematics but its labeled different because i think you gave me the schematics of the paper scratch, right?

No, this is the trace of my actual Ripped Speaker.

The component locations should be similar unless there has been a PCB revision.

 

[CrustyD3mon]

ahh gr8.

No, this is the trace of my actual Ripped Speaker.

The component locations should be similar unless there has been a PCB revision.

you're right, i confered now, its the same, i was the one mistaking with the paper scratch one that i already had here.

C15 on this circuit its used for what? Just asking because when i was probing for the first time, it was the only polyester capacitor that in one of the legs produced no sound...