Klon Clone, dual gang gain pot randomly switches direction

[LordVoltemort]

Hi, long time listener, first time caller here. I've been making DIY pedals for a few years now. Made one based off a Klon circuit that I've been really happy with. Even made a bunch of them for friends that liked it. Around 20 total. Well, a few of them(3) have come back to me with the same issue. After a few weeks or months of use, the Gain Potentiometer all of a sudden flips. 1 = full gain and 10= low gain as opposed to how it normally works which is standard 1= low gain, 10-high gain. It's the weirdest thing. The PCB is of my own design. I've tried changing out the pots but to no avail. I tried changing out the IC's that contains the gain op amp. Nothing. I don't even know how it's possible to be happening. If it stopped working all together, that would be easy, but it's as if the lugs spontaneously reconnect themselves backwards or something. Any ideas of things I could check would be great. I haven't seen this issue in any other forum and since it isn't happening to a majority of these and isn't happening from the start, I'm at a loss. Thanks a lot for any help.

[Slowpoke101]

Welcome to the forum. Many of us were long-time readers before actually joining. It's a great place and a lot of fun.

Now, your gain control problem. Gain randomly reversing seems like an interesting problem and possibly quite annoying.
Check that the Vref (4.5V ) that directly connects to the dual gang pot is in fact still there and the correct voltage.
Measure the voltages on all the ICs (when the fault is present ) and post them here.

But first have a look at the debugging thread and see if it helps - It does help us greatly for the type of info needed for remote diagnostics.
https://www.diystompboxes.com/smfforum/index.php?topic=29816.0

[LordVoltemort]

Excellent, I'll give all this a look and report back what I find. Thanks a lot!

[duck_arse]

also welcome, just so's I can ask - is there any tantalum caps on your boards?

[LordVoltemort]

No Tantalum Caps. All multilayer ceramic, film or electrolytic. I am using germanium diodes for clipping and standard metal film resistors.

Ok, I've done just about everything I know how to do and still the problem persists. When I first opened it up the voltages were all over the place and the Gain pot wasn't showing 100k of resistance. It was odd, the resistance on both sets of lugs would only reach about 26k Ohms and it would reach it in the middle of the dial, them it would die back down to zero as I kept turning it. So I replaced both the Voltage Converter IC and the Gain Pot with new ones. All voltages after that were where they should be. 4.5v on the fully functional new pot with full 0-100k Ohm's of resistance front to back. 9v-ground rails on the IC containing the first two Op Amps which includes the gain stage Op Amp. Approx 18V and -9V rails on the second IC. However, the problem still persisted exactly as before. So the first thing I did was check continuity/resistance/capacitance of literally every part and path on the board and replace the IC's with new ones. Everything looks exactly like it should. I checked it against the readings of a different, fully functional pedal just to see if I was missing something. They are identical. Since it's only happened randomly in a small percentage of this particular pedal I'd build and since they all worked properly for a while before the malfunction, I'd assume it was a parts issue. But after replacing with new parts and checking all the parts in the box and finding no damage and finding the PCB still functioning, I'm scratching my head. The only parts I couldn't test very well were the multilayer ceramic caps in the board.

[LordVoltemort]

Update: Looks like this might be just a case of human error. Upon examining the two pedals that came back, I immediately noticed that I hadn't totally soldered on the pots. What an idiot. Anyhow, when I soldered one back up fully and checked all the voltages, everything was correct and it immediately started working correctly. The other one however didn't. Even after I'd switched out IC's for new ones and tested the entire board for continuity, it didn't work. So I decided to remove every single component and put them all on a new board. Took like 6 hours! Anyhow, it worked perfectly after that. I think when I didn't fully attach all the pots, it caused something to overheat which I think damaged one of the IC's and it damaged the circuit board or vice versus. Anyhow, hopefully that's that. Thanks for the help y'all.