SOLVED Yet Another Kliche Situation (Bypass is not awesome)

[smalltownsongs]

Hey all!

Well over 50 builds under my belt, including quite a few klones, but this is my first self-unsolvable issue, so I figured I'd post up and graciously ask if y'all could see something I'm just missing.


Engaged, it's loud and sounds pretty good (I might say it's not as overdriven as I'm used to though), and in bypass it's muffled, and the signal is just fighting to get through. It has some crackle to the lower turns of the gain pot. I did have this boxed up and it had the same issues (verified it wasn't the gain pot grounding out), but de-boxed for reflow and pics.

What I've done:
- Visually checked and verified I had the right values (feel free to double or triple check me tho! that all-tan-no-bands fella is the 422k, have used em before).
- Visually checked for hairline solder bridges or anything touching.
- Reflowed all solder joints
- Measured voltage of the IC chips

Pics:

IC Voltages:

1044

1. 9.45
2. 4.81
3. .2
4. -4.44
5. -9.04
6. 4.50
7. 5.99
8. 9.45

TL072 (Middle)

1. 4.02
2. 3.55
3. 3.55
4. -9.04
5. 3.54
6. 3.54
7. 3.06
8. 17.05

TL072 (Right)

1. 2.91
2. 2.91
3. 1.16
4. .1
5. 2.53
6. 2.50
7. 2.30
8. 9.45

I was planning on picking up another Kliche bypass breakout board and redoing that and the switch to see if that would help, but was waiting to place a larger order to make it worthwhile. Def don't want to true bypass it.

Any and all help and guidance is appreciated!

 

[jimilee]

Sounds like it’s time for the audio probe.

 

[smalltownsongs]

Sounds like it’s time for the audio probe.

OOoh, yes, that was another plan too.
I've not used one to date, but will do some searching.

 

[z2amiller]

I think something's wrong around VREF. Pin 3 and 5 of IC2 (middle) are both tied directly to VREF and they're showing 3.5V instead of something around the 4.7V mark I'd expect at 1/2 of 9.45V. Pin 3 of IC1 (right) is also tied to VREF through a 1M resistor and is only 1.16V which would muffle your buffered output. It looks like the voltage divider resistors are indeed both 27K (but double-check since it's always a little hard to tell colors from a photo) so maybe it's something else that ties to VREF that is being shorted somewhere. Unfortunately one of those somewheres is the really-hard-to-desolder-without-destroying-stuff dual-gang pot that you say is scratchy (sus).

Check R2 and R31 maybe? R31 looks like it might be 10M and not 1M - green and yellow can be hard to tell apart tho.

 

[Coda]

Insulate the dual-gang…

 

[swelchy]

I'm, with Coda..... If the dual gang rivets can play scratchy scratchy with the pcb surface and go through the coating ,touch the traces and short out all kinds of overdrive fun... I made some 3d printed dual gang pot covers just for this and shared them on thingiverse for the interwebs to use how they like... 50 % of kliche issues in the troubleshooting thread probably relater to this issue alone... 40% bad soldering.. 10% a component wildly out of place from not paying attention to correct value or spot on the pcb..

 

[Coda]

I'm, with Coda..... If the dual gang rivets can play scratchy scratchy with the pcb surface and go through the coating ,touch the traces and short out all kinds of overdrive fun... I made some 3d printed dual gang pot covers just for this and shared them on thingiverse for the interwebs to use how they like... 50 % of kliche issues in the troubleshooting thread probably relater to this issue alone... 40% bad soldering.. 10% a component wildly out of place from not paying attention to correct value or spot on the pcb..

80% of the time it’s the dual-gang pot everytime…

 

[andrewsrea]

It appears to be a resistive leak of Vref, which could be caused by the concentric gain pot's pins shorting to ground, or a defective TL072, possibly a fault in the voltage divider or leads of the Vref.

If insulating the gain pot doesn't fix it, try pulling IC1 and IC2 from their sockets (power unplugged) and the adding power, measure the Vref on pins #3 for both sockets and pin #5 on the IC2 socket to see if it is around 4.7V. If it measures 4.7, one of the pulled ICs is defective. To figure out which, add one back and measure the voltages. If it is still good, pull that one and add the other back and measure.

If by pulling both ICs, it still has erroneous Vref values, check all Vref destinations for resistance to ground. It should never be more than R26 (27K). Look for resistive paths to ground. Note that if there were shorts to ground, Vref would be zero.

My gut tells me it is IC1 or the pot pin insulation.

 

[smalltownsongs]

I think something's wrong around VREF. Pin 3 and 5 of IC2 (middle) are both tied directly to VREF and they're showing 3.5V instead of something around the 4.7V mark I'd expect at 1/2 of 9.45V. Pin 3 of IC1 (right) is also tied to VREF through a 1M resistor and is only 1.16V which would muffle your buffered output. It looks like the voltage divider resistors are indeed both 27K (but double-check since it's always a little hard to tell colors from a photo) so maybe it's something else that ties to VREF that is being shorted somewhere. Unfortunately one of those somewheres is the really-hard-to-desolder-without-destroying-stuff dual-gang pot that you say is scratchy (sus).

Check R2 and R31 maybe? R31 looks like it might be 10M and not 1M - green and yellow can be hard to tell apart tho.

These are all good and proper, thank you for the suggestions!

 

[smalltownsongs]

I'm, with Coda..... If the dual gang rivets can play scratchy scratchy with the pcb surface and go through the coating ,touch the traces and short out all kinds of overdrive fun... I made some 3d printed dual gang pot covers just for this and shared them on thingiverse for the interwebs to use how they like... 50 % of kliche issues in the troubleshooting thread probably relater to this issue alone... 40% bad soldering.. 10% a component wildly out of place from not paying attention to correct value or spot on the pcb..

80% of the time it’s the dual-gang pot everytime…

I'd checked the dual-gang as that seemed to be the most popular issue. It's not touching, and I've actually used a half of a guitar pick to put in the gap as a shim of sorts when I had it boxed. This issue is still happening "outside" of the enclosure, no dual-gang touchy-touchy. I won't rule out something happening that I can't quite see yet (maybe an errant solder bridge), but I'll work on pulling the ICs and testing first then maybe replace the dual-gang, as not-fun as that seems haha.
Thank you both for the suggestions!

 

[falco_femoralis]

You're going to want to audio probe it and investigate the area where the signal drops out along the bypass signal path.

The signal having crackle when the gain pot is low is a clue that AC and DC voltage are mixing when they shouldn't. I would check all the pins of your IC sockets and see if there is continuity where there shouldn't be.

 

[smalltownsongs]

You're going to want to audio probe it and investigate the area where the signal drops out along the bypass signal path.

The signal having crackle when the gain pot is low is a clue that AC and DC voltage are mixing when they shouldn't. I would check all the pins of your IC sockets and see if there is continuity where there shouldn't be.

Thanks, the socket being a problem makes sense to me, as I didn't have the regular sockets I prefer and used ones that I kinda hate.
To clarify, should there be continuity at all?
Thanks!

 

[smalltownsongs]

It appears to be a resistive leak of Vref, which could be caused by the concentric gain pot's pins shorting to ground, or a defective TL072, possibly a fault in the voltage divider or leads of the Vref.

If insulating the gain pot doesn't fix it, try pulling IC1 and IC2 from their sockets (power unplugged) and the adding power, measure the Vref on pins #3 for both sockets and pin #5 on the IC2 socket to see if it is around 4.7V. If it measures 4.7, one of the pulled ICs is defective. To figure out which, add one back and measure the voltages. If it is still good, pull that one and add the other back and measure.

If by pulling both ICs, it still has erroneous Vref values, check all Vref destinations for resistance to ground. It should never be more than R26 (27K). Look for resistive paths to ground. Note that if there were shorts to ground, Vref would be zero.

My gut tells me it is IC1 or the pot pin insulation.

OK, we're getting somewhere here... where, I don't quite know, but perhaps somewhere.
I unplugged power (I'm using the PedalPCB auditorium rig for power at the moment), and pulled IC1 and IC2. Plugged the power back in and
Pin #3 and #5 for IC2 are 4.7V however... Pin #3 for IC1 is whack. It kinda reads all over the place then simmers down to 2.3mV.
I removed the crap socket, inspected all over for traces of any issue, ISO cleaned it, and put in one of the sockets I like there.
No difference, same weird read. Should I pull the dual gang for good measure as well, or might this weird reading show something else?

With only IC3 in, here are my readings for the IC1 socket:

1. 4.74
2. 4.74
3. 2.3mV
4. 0
5. 4.72
6. 4.70
7. 4.47
8. 9.48

Pins 1 & 2 on IC1 have continuity.

 

[falco_femoralis]

Pins 1 and 2 of IC1 having continuity is ok.

I agree with the VREF issue, it should be higher than 3.5, but the gain pot scratchy issue could be that it's leaking DC into the audio path somewhere.

The back of the gain pot does not contact the PCB in this case

I believe the weird reading on the meter is a result of the meter loading pin 3 when measuring it. The fact that you now have 4.7v at pins 3 and 5 of IC 2 is good. I would put both IC's back in and test the board thru the amp at this point. If it's still weird, then change the other socket as well.

 

[andrewsrea]

I agree with @falco_femoralis , that continuity for IC1, Pins #1 & #2 are normal. It is a buffer and that is normal for a buffer.

I think the 2.3mV on IC1 Pin #3 is the DVM reading its own spurious voltage. IMHO, there is a short to ground at the junction of C1, R2 & Pin#3
-or- R2 is open (infinite resistance), -or- R2 is not making contact with Vref on the 'feed' side.

With the power off and IC1 un-socketed, measure continuity to ground from Pin#3. If it beeps, you have a short in that compartment of the circuit. If not, power up and measure voltage to the feed side of R2. If it measures close to 4.7V, then unsolder the leg of R2 which goes to Pin#3 and lift that leg from the solder pad and measure the voltage for 4.7V. If there is not, replace R2 with a 1M.

Looking at the picture, also check between the solder joint of R2 and C6, on side by the gain pot. It looks like there could be a hair of stray solder connecting the two.

For the scratchy gain pot, there should be equal Vref at each lug of Gain1 and Gain2, with IC1 installed, which makes the voltage potential (difference pin to pin) thru the pot 'zero'. It will likely go away when fixing IC1 Pin#3. A little contact cleaner in both sections of the gain pot for insurance, doesn't hurt.

 

[smalltownsongs]

Pins 1 and 2 of IC1 having continuity is ok.

I agree with the VREF issue, it should be higher than 3.5, but the gain pot scratchy issue could be that it's leaking DC into the audio path somewhere.

The back of the gain pot does not contact the PCB in this case

I believe the weird reading on the meter is a result of the meter loading pin 3 when measuring it. The fact that you now have 4.7v at pins 3 and 5 of IC 2 is good. I would put both IC's back in and test the board thru the amp at this point. If it's still weird, then change the other socket as well.

I agree with @falco_femoralis , that continuity for IC1, Pins #1 & #2 are normal. It is a buffer and that is normal for a buffer.

I think the 2.3mV on IC1 Pin #3 is the DVM reading its own spurious voltage. IMHO, there is a short to ground at the junction of C1, R2 & Pin#3
-or- R2 is open (infinite resistance), -or- R2 is not making contact with Vref on the 'feed' side.

With the power off and IC1 un-socketed, measure continuity to ground from Pin#3. If it beeps, you have a short in that compartment of the circuit. If not, power up and measure voltage to the feed side of R2. If it measures close to 4.7V, then unsolder the leg of R2 which goes to Pin#3 and lift that leg from the solder pad and measure the voltage for 4.7V. If there is not, replace R2 with a 1M.

Looking at the picture, also check between the solder joint of R2 and C6, on side by the gain pot. It looks like there could be a hair of stray solder connecting the two.

For the scratchy gain pot, there should be equal Vref at each lug of Gain1 and Gain2, with IC1 installed, which makes the voltage potential (difference pin to pin) thru the pot 'zero'. It will likely go away when fixing IC1 Pin#3. A little contact cleaner in both sections of the gain pot for insurance, doesn't hurt.

Thank you both SO very much!

@falco_femoralis I changed out the other two sockets just cause I could.... and VOILA. We have a working, non-scratchy Kliche!
This is the ~15% that wasn't a grounded-out dual gang, but rather using substandard parts. While I do feel a bit foolish there, I'm sure I'm not the first one to have such a moment, and thanks to the kindness of this forum, I've gained more knowledge. MUCH more knowledge. Eventually I'll learn how to use an audio probe, but not today.
My sincerest thanks
-Kris

 

[Erik S]

Thank you both SO very much!

@falco_femoralis I changed out the other two sockets just cause I could.... and VOILA. We have a working, non-scratchy Kliche!
This is the ~15% that wasn't a grounded-out dual gang, but rather using substandard parts. While I do feel a bit foolish there, I'm sure I'm not the first one to have such a moment, and thanks to the kindness of this forum, I've gained more knowledge. MUCH more knowledge. Eventually I'll learn how to use an audio probe, but not today.
My sincerest thanks
-Kris

View attachment 105387

Cool graphic!

Glad you got it working.