KLON clone, even with Gain knob at 10 it never breaks up. Why?

[half_smith]

Those off-board resistors are on your schematic.

You're right I see them now. thanks

Any DC gain higfher than unity "upsets" op-amp output from sitting on Vref, according to superposition theorem..

thanks Antonis, for not pulling any punches 

When the pot is turned CCW (wiper to terminal 1), the signal at R6 is being sent to VB and the Opamp non-inverting input is getting nada. Nada in, nada out.

When the pot is turned CW, the signal at R10 is going to VB, which means the inverting input is "seeing" a weak signal, and the opamp does its "magic" to amplify and bring it back up.

very super helpful to have this explanation.
The R10 branch of feedback was really messing with my head.
That pot is kinda funny because the VB is in the middle with R6 on one side, R10 on the other. I think Antonis originally suggested the R10 side? I'll experiment a bit.
Can I use an Electrolytic here or would NP be better? Which way to orient? My guess is + is facing R10?

Just snip the wire to the gain pot wiper, (the side of the gain pot that controls the OD gain, the one attached to R6 and R10, labeled "b" in your schematic/layout)
and put a cap, maybe 47n, maybe 1uf, between the ends of the cut wire.

Thanks for the step by step here, I had tried inserting a Cap at various places around there but hadn't thought of that easiest approach, I will do that next.

*disclaimer for my pics, this was one of my first builds I'm finally revisiting, and  I have torn this thing apart multiple times. It looks pretty scratched up on the bottom, but the same essential issue has persisted since the first build when it was all clean.
Also, when I rewired it, I added eyelets because I wasn't able to easily clean the holes well enough to get stranded wire through.
And I've socketed many parts as I've been troubleshooting.
You're probably going to say I've got to put the blood of an orange on the altar at midnight on a Tuesday...

[antonis]

Solder side looks OK but items one looks like a bit of mess..
(especially the upper PCB part for pots/cables wiring..)

P.S.
There are several resistors of pads spacing enough for laid flat where you've placed them flying..

[half_smith]

Antonis, yes the wiring got really messy so I made eyelets for each, it looks worse in the pic, but they are solid and not touching.

[half_smith]

with a .1uf cap (metal film) between Pot-b and R10
AND Simultaneously
a .1uf cap sistered to R12

...

no change.

[idy]

Not where I suggested. No Caps between Rs and the pot. Cap from wiper to board.
Snip wire to wiper (terminal 2)
attach cap to both ends of snipped wire.
Try
It.

Yes metal film, don't need to worry about polarity.

Picture: White wire from pad marked A2 seems to go nowhere?

[idy]

Two places on board that need jumpers but I don'w see them.... it also looks like there are traces...9next to R5, R24)... and there another. Confirm continuity or add jumpers.

[half_smith]

Idy, thanks for your reply!

Snip wire to wiper (terminal 2)

Please look at the segments I posted today, the Dual Gang Pot B p2 is jumpered to Pot A p3 [VB]
There are two wires going to the board, B1, B3 - I've tried placing a .1uf np cap where the wire meets the board in either, both B1, B3 with no change.
Are you saying to put the cap between PotA-p3 and PotB-p2 ?

Two places on board that need jumpers but I don'w see them.... it also looks like there are traces...9next to R5, R24

These jumpers are traced on the top side
*****************
As I wipe to the Gain side (CW) it definitely dips in volume, like there is a sag or drain somewhere over there... I'm looking, again.

[idy]

Whatever is going to pot b terminal 2. The wiper. Snip that wire. Since it is also pot a terminal 3, just run a cap instead.

to repeat:
Cut the wire between a3 and b2. Put a cap there instead. This is an attempt to implement Antonis' suggestion, I think. To keep DC gain to unity.

Did you confirm that those (3) places that need jumpers on the doc, and lack them in your build, really are connected? Tested for continuity with a meter?

You didn't answer,

Picture: White wire from pad marked A2 seems to go nowhere?

It should go to pot a2. Yes? No?

[idy]

I am skeptical of the cap to vb helping. That connection to vb is the only bias the opamp has I think. It is a weird arrangement. I wish a Klon lover would clarify it for us. I think if you put the cap in the opamp will gate. But it is an easy experiment, and easy to reverse...

[half_smith]

SOLVED!

There was another trace that wasn't making continuity.
I started a complete walk through the circuit and lo and behold

crucially the traces that needing bridging were right in the Op Amp feedback loop.

[idy]

Praise Ohm.

[half_smith]

*UPDATE*
The pedal is working great, but...

If I turn the GAIN knob all the way off (CCW) I get a noticeable ever-present, almost swirly squeal.
Only when I turn it all the to the end - the squeal stops as soon as the pot is set anywhere but 0

Any guesses?

[antonis]

Instead of various guesses, why don't you put a resistor in series with pot..??