unicab aka the sizzling kettle

[makisushi]

Any idea what could cause this kind of noise? Sometimes the pedal works fine, sometimes it start doing this weird noise... I tried to change the ICs, reflow, change power supply, clean the pcb with isopropyl alcohol, but no differences. It seems to get worst the longer the pedal is powered on.

 

[AceHyzer]

You have to turn the pedal off *before* the kettle reaches the boiling point.

 

[AceHyzer]

But in all seriousness. What are you using to power it? Power supplies are very often the culprit of noises like that.

Does the pedal work at all if you play into it? Or does it just give those screechy noises and nothing else?

Also, I can’t tell for certain, but the output jack does have a ground connection, correct?

 

[AceHyzer]

Ah I see you said you’ve tried power supply. Have you tried putting a buffered pedal before it? Sometimes that can fix issues as well.

 

[makisushi]

Yes sometimes the pedal works just fine and than this. I build around 3 pedals per week and two pedals that was built in the same week have a similar issue. I used a weird flux that week (AliExpress ). the board is still a bit sticky after brushing it with a tooth brush and alcool . I wonder if the AliExpress flux could be the cause ?

 

[jwin615]

You have a lot of excess cable flying around in there. Input right over the top opamp is suspect
Try moving some that around as it's oscillating to maybe induce a change in the oscillation.
May or may not be the problem but with all that wire and 6 gain stages, it may be.

 

[makisushi]

You have a lot of excess cable flying around in there. Input right over the top opamp is suspect
Try moving some that around as it's oscillating to maybe induce a change in the oscillation.
May or may not be the problem but with all that wire and 6 gain stages, it may be.

It does the same thing out of the case with the wires away from the PCB .

 

[makisushi]

But in all seriousness. What are you using to power it? Power supplies are very often the culprit of noises like that.

Does the pedal work at all if you play into it? Or does it just give those screechy noises and nothing else?

Also, I can’t tell for certain, but the output jack does have a ground connection, correct?

yes grounds are there. I just unplugged the pedal and plug it back and it works perfectly, no noise at all...If I leave it plugged in, I'm almost sure that the kettle will start sizzling again. this is driving me nuts lol

 

[makisushi]

yeah so i didn't touch the pedal for 20 minutes and now it's noisy (but still not sizzling). like vinyl crackling noise

 

[makisushi]

You have a lot of excess cable flying around in there. Input right over the top opamp is suspect
Try moving some that around as it's oscillating to maybe induce a change in the oscillation.
May or may not be the problem but with all that wire and 6 gain stages, it may be.

It might actually be related to the input hot wire. I know the cable is not shielded but should it be that sensitive when I touch it?

 

[Nostradoomus]

shorten up as many of those wire runs as you can and report back, run them under the board as far from any opamps as they will get. What's happening after the output jack there? Is that an adapter with a 3.5mm cable or?

 

[makisushi]

shorten up as many of those wire runs as you can and report back, run them under the board as far from any opamps as they will get. What's happening after the output jack there? Is that an adapter with a 3.5mm cable or?

Will do that this weekend and report back . Yes theres an adapter on the second video because I was using a stereo pedal before plugging this one

 

[makisushi]

I must also add that if I bypass the effect the noise disappear

 

[jwin615]

That seems a little sensitive but again, it has six gain stages. That's just the natural radiation from your body. Same thing as when you play single coils and your guitar is less noisey when you move it away from your body.
Unless you have some cheap wire that has an insulator that isn't actually insulating.
Now, touching the shield of the jack resulting in noise is odd.
That makes me thing your jack is floating(ungrounded) or you have a coupling of signal to ground

 

[makisushi]

I grounded both in and out with the PCB, the case is bare metal so it's also ground. The noise still appear when the effect is out of the case . I will still shorten the wire to give it a try

 

[Erik S]

In that last video it looks like your input jack isn’t tightened down to the enclosure. Possible that could contribute to the ground noise when touching the input wire if the jack isn’t making consistent ground contact.

 

[makisushi]

Yes true it was loose from testing it outside the case .

 

[makisushi]

so i removed the pcb from the enclosure, same thing: Pedal works fine for a while, and start to make noise after several minutes. If I bypass the pedal, no noise. wires is away from the pcb and doesn't seems to be the problem. It's really a popping crackling noise now. I also use the same wires and connectors on others pedals with no issue


It must by something on the pcb... I think I'll soak it again in alcohol. There's some weird white stuff on it that keeps coming back even if i brush it. I don't know whats going on there, flux residue, corrosion?

 

[jwin615]

Measure the voltages at the ICs with it "cold", then again with it bugging out.

	IC1		IC2		IC3
Pin	Cold	Hot	Cold	Hot	Cold	Hot
1
2
3
4
5
6
7
8

After it's been noisy for a bit, touch each opamp and see if any feel warmer.
Audio probe in this order and see if you can hear where the oscillation/noise starts. Feed it a test tone or looper while doing so.
IC1 Pin 3
IC1 Pin 1
IC2 Pin 3
IC2 Pin 1
IC3 Pin 3
IC3 Pin 1
IC3 Pin 5
IC3 Pin7
IC2 Pin 5
IC2 Pin 7
IC1 Pin 5
IC1 Pin 7
You can really do any order, but that's the order from input to output. Once you hit the noise, it will be in every point after that.
If the noise seems to be everywhere, maybe start checking pins 4 and 8 of each IC.

 

[mybud]

As for cleaning the board by soaking it with alcohol, don’t allow any cleaners into switches or pots.

Better still, use cotton buds or the like soaked in IPA or flux cleaner and gently wipe the affected areas clean.