Imp v2 tone knob

[redkurn]

Decided today to check the tone knob since it hasn't worked since I boxed it... pot tests good, testing from solder point on main pcb.

What could be the culprit of not getting any play through the pedal for tone?

I would think bad cap, but it was fine until I boxed it and I assumed I broke the pot when I pulled on it a little aggressively.

Edit:
Pulled everything out of the box except the power/audio jacks, tone still isn't working and wiring appears fine, no obvious sign of it having grounded.
Thinking bad cap?
Which cap controls tone, I see a few in the trace diagram, looking at C13 and C14.

[madbean]

Both C13 and C14 are responsible for tone shaping but C14 is the "tone cap". Are you getting output despite the tone knob not working? How about your voltages on IC2A and IC2B? Do those look similar to the ones in the doc?

[Zerro]

Maybe pot's track has crackle at one end. You won't see it but it is there, mostly very tinny. Controll with r-meter while slightly moving with pin.

[redkurn]

Both C13 and C14 are responsible for tone shaping but C14 is the "tone cap". Are you getting output despite the tone knob not working? How about your voltages on IC2A and IC2B? Do those look similar to the ones in the doc?

I get sound, volume knob works and gain also works very well. Which is partly why I waited so long to fix the tone.

IC1, IC2 all voltages are in spec. Some are .1v lower than expected
IC3 pin 7 is 7.1v when expecting 5.88, so 1v over expected.
Tone knob shows signs of a full sweep, from 0.6 ohm to just over 10k.

If I recall correctly this started after I boxed it the second or third time, had wiring break between the controls and mainboard.
One day I may replace with short ribbon cable or something stronger that can be shaped.

Maybe pot's track has crackle at one end. You won't see it but it is there, mostly very tinny. Controll with r-meter while slightly moving with pin.

Pot is dead silent, has full sweep.

[redkurn]

Caps test as good as day 1 install...

I could try my make shift audio probe and see if anything happens.

Not finding a loss of audio on IC1 or IC2, A points for the daughterboard to connect to are fine, followed the tone path and it's getting signal, but nothing on the tone pot turns does anything.

I do have a 100k I could use to test swapping or parallel...?

No difference.

I can't find a problem before or after the tone pot.

[Zerro]

If pot is ok and parts too, focus at continuity of pcb tracks - maybe crackles in it, mostly around solder points.

[redkurn]

If pot is ok and parts too, focus at continuity of pcb tracks - maybe crackles in it, mostly around solder points.

I've checked around them and they appear fine, I was quick while soldering and didn't overheat.

I'm thinking is it possible for ic2 to appear to be functioning correctly, but damaged in some way?
I would think there would be no audio passing through the chain if something were damaged, I've probed with a diy audio plug and can follow sound through the tone circuit.
If I read the schematic properly input>gain>tone>output and I can clearly hear the gain side when probing through the tone stack and clean when probing from the beginning.

There has to be something damaged, maybe the input Jack came into contact after being boxed and shorted something in that area, which is why I am looking at ic2.

I used standard 1/4 jacks and input I drilled a couple millimeters higher and it's really close to the pcb.

I am thinking would to be possible to temporarily remove ic2, jumper into a breadboard and somehow test with normal transistors?

Friend gave me a few, I haven't looked them up yet, but I do want to narrow down what could be faulty and he thinks it's possible that I didn't fry it.

[Zerro]

Very good idea - audioprobe, and trace it from start.

[madbean]

A couple of pics of the top and bottom of the build would help, too.

[redkurn]

A couple of pics of the top and bottom of the build would help, too.

I'll take it apart again and take some pics, quote you again when I get it done.

[redkurn]

A couple of pics of the top and bottom of the build would help, too.

Attached.

Considering taking all the wiring off, reboxing and using thick resistor legs to permanently mount the control board to the main board or something more sturdy.

[jimilee]

Did you get an audio probe made? Troubleshooting a tone issue is only a couple of parts. You did mention a possible faulty pot.


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[redkurn]

I did, traced it all around and through the tone pot.

Tested the caps associated with tone, everything seems to be working, the pot resistance changes when turning, but no change to the sound.
I'm guessing something happened to IC2 when I boxed it and it hit a short, but hoping that isn't the case because we all know the pain of removing a IC...

[jimilee]

I did, traced it all around and through the tone pot.

Tested the caps associated with tone, everything seems to be working, the pot resistance changes when turning, but no change to the sound.
I'm guessing something happened to IC2 when I boxed it and it hit a short, but hoping that isn't the case because we all know the pain of removing a IC...

Probe IC2 pins 1,2 6 and 7. You should have audio on them. You should be able to probe the legs of the tone pot to see if there's any change. A tone circuit is just a resistor or two and one sometimes two caps. Have you checked your resistor values intuit area?

[redkurn]

I did, traced it all around and through the tone pot.

Tested the caps associated with tone, everything seems to be working, the pot resistance changes when turning, but no change to the sound.
I'm guessing something happened to IC2 when I boxed it and it hit a short, but hoping that isn't the case because we all know the pain of removing a IC...

Probe IC2 pins 1,2 6 and 7. You should have audio on them. You should be able to probe the legs of the tone pot to see if there's any change. A tone circuit is just a resistor or two and one sometimes two caps. Have you checked your resistor values intuit area?

Resistor values are right, this started after boxing.
I have audio throughout the circuit, before, after tone, at IC2 on all pins.

Right now I am taking it apart, going to clean, look for any signs of fault and solder it back together better since I did this nearly a year ago.