SOLVED Kliché Mini - Gain works weirdly inverted

[Ralfonso]

Hi everybody,

I am building a Kliché Mini at the moment. Unfortunately, the Gain poti works not as expected.
If it is turned most left, I get the most clipping. The further right it is turned, the less clipping can be heard. Instead it gets dark.

I already double-checked the resistor and capacitor values.
The voltage supply of the ICs seems to be ok as well.
I have no idea what to try next.

Here are the voltages of th ICs:

IC1 (TL072)
1 = 4,73V
2 = 4,73V
3 = 1,29V
4 = 0,00V
5 = 4,62V
6 = 4,72V
7 = 4,69V
8 = 9,46V

IC2 (TL072)
1 = 4,76V
2 = 4,73V
3 = 4,67V
4 = - 8,98V
5 = 4,68V
6 = 4,73V
7 = 4,69V
8 = 17,0V

IC3 (TC1044SCPA)
1 = 9,46V
2 = 4,95V
3 = 0,00V
4 = - 4,29V
5 = - 8,98V
6 = 4,73V
7 = 4,33V
8 = 9,46V

Thanks a lotfor your help.
Greets Ralf

 

[Coda]

How well were you able to insulate the dual-gang pot?...

 

[Ralfonso]

What are you trying to tell me?

I added a sticking insulation patch at the bottom (although the pot is not above the PCB anyways).
And normally the pots are not insulated against ground, right?

The 6 pins do not touch anything else.

Or did you aim for something else?

 

[Coda]

What are you trying to tell me?

I added a sticking insulation patch at the bottom (although the pot is not above the PCB anyways).
And normally the pots are not insulated against ground, right?

The 6 pins do not touch anything else.

Or did you aim for something else?

From my experience, dual-gang pots have a tendency to short out. When they do, it often causes the pedal to behave strangely. When I built my Kliche, the volume control worked in bypass, and there was no effect when engaged…

 

[Ralfonso]

To test the dual gang pot, I desoldered it an measured it with my DMM.
I get infinite resistance between the first and the second channel. So it seems that this is not the issue.

Interestingly, instead of 100K it has ony 86K. But would this justify the inverse behavior?

 

[giovanni]

The pot seems ok. Did you try putting a thick piece of plastic between pot and board? A short seems plausible.

 

[fig]

It appears you have an incorrect value in D4. Was this an intentional mod? The voltage @ IC2-8 is a tad low.

 

[Robert]

Double check the values of R6 and R13. They may be correct (we were just recently discussing inconsistencies in resistor color codes) but they look an awful lot like they could be 11M instead of 1K5, depending on how you read them.

Is the wider band the tolerance band, or is it the one spaced furthest away?

 

[Deperduci]

I'm going to ask the extremely stupidly obvious question, with the joys of getting dual gang pots from some vendors.... do you have the wrong taper pot? it's not on you if THEY sent you a c(antilogrhythmic) taper instead of a b(linear)

I seethe markings but is it right in the gutz?

 

[Ralfonso]

It appears you have an incorrect value in D4. Was this an intentional mod? The voltage @ IC2-8 is a tad low.

Do you mean R4? I did not change anything from the original components.

 

[fig]

Do you mean R4? I did not change anything from the original components.

D4. It looks different than the 1N4001 beside it.

 

[Ralfonso]

Double check the values of R6 and R13. They may be correct (we were just recently discussing inconsistencies in resistor color codes) but they look an awful lot like they could be 11M instead of 1K5, depending on how you read them.

Is the wider band the tolerance band, or is it the one spaced furthest away?

I measured them. They have 1K5 Ohm. So they seem ok

 

[Ralfonso]

D4. It looks different than the 1N4001 beside it.

They are identical, just oriented differently.

 

[Ralfonso]

Hello again,

after a few hours of searching, there is still no improvement...

In the meantime I have built an audio probe and found out that the signal at IC1.1 still sounds good at pin 3, but it sounds much duller after the first amplifier stage.
So in the circuit diagram IC1.1 at pin 1. The same with IC1.2 at pin 7.

I swapped the ICs around. Same behavior. I even installed another TL072. Same behavior. I think that we can therefore exclude a broken IC.
So I assumed with my half-knowledge that the IC is amplifying the wrong frequencies and I started to measure all the resistors and capacitors in the feedback loop of IC1. In both cases, I even removed and measured the components that coudn't be measured when installed. All values are OK.
Now I've gone through all the resistors and capacitors - they are all correct.

Next I removed the germanium diodes. even without clipping diodes, the whole thing sounds dull after the 1st amplifier stage.

I just can't figure it out...

Greetings Ralf

 

[Ralfonso]

My latest change: I exchanged the dual-Gang pot with two B100K pots.
This gives me the impression, that one doe NOT AT ALL effect the sound. This is weird. I will continue my search from here…

Could it be that the PCB has a shortage or a interrupted connection? How likely is something like this from PedalPCB’s PCBs?

Greets Ralf

 

[Ralfonso]

Found it!

After yet another test with my audio probe, I was wondering, why I hear something before R12, but ont after it.
So there was a grounding! See the attached image.

Thanks to all for trying to help me!

Greets Ralf

 

[Coda]

Definitely sounded like a ground issue. I’m not sure if any other circuit is as susceptible to this than the Klon…you see it often with Klon troubleshoots. If the pedal is acting strangely (working, but not working correctly), and the circuit is a Klon, it’s most likely something grounding out…

 

[giovanni]

When I built my KOT, the pots were shorting on the led bezels and I was getting similar symptoms (tone acting like volume or something). These are the trickiest issues to find!

 

[Ralfonso]

These are the trickiest issues to find!

For sure. I wasted so many hours for this thing...

 

[MichaelW]

For sure. I wasted so many hours for this thing...

Glad you found the issue! A good case for always tinning stranded thread wire. Part of the reason I’ve moved to using solid core whenever I can.

You can also mark this thread as “solved” by editing your original post and select thing from the thread drop down menu the “solved” badge. Helps with the hygiene of this forum!