Volume jumps on pedal

[bird]

Pedal was working fine for 6 months. Now it will intermittently go full volume. My friend was using it and in the last week noticed a louder than usual pop when it engaged. More recently, it would engage and the volume would be super loud once in a while. While debugging it today, I got it to do the volume jump after it was already engaged (although, I don't know how I got it to do that...).

The pedal is a Wampler Pinnacle from the Effects Layouts layout (https://effectslayouts.blogspot.com/2017/04/wampler-pinnacle.html). I finished it in about 6 or 7 months ago, and my friend was using it regularly since then. I've never encountered a problem like this.

Here's a list of things I've tried in the last 4 hours of troubleshooting:
-Switched guitars, cables, power supplies, and houses.
-Switched transistors (had a few new ones to swap in, changed the rest around.
-Voltages at transistors and other points seem normal (9+ in, 4-4.5 at transistor drains).
-Tried a new 3PDT switch.
-I've tried the circuit fully installed, pulled out from the enclosure to make sure there were no accidental grounds with off board components as separated as possible.
-Checked ground continuity everywhere.
-Tried with pots and switches in all positions, no difference.
-Checked all connections to output and volume pot, all good.
-Checked resistance on volume pot - seems normal even when it jumps to full volume. This made me think something is shorting to the output and bypassing volume, but I can't find any evidence on the circuit.

Sometimes just lightly touching with minimal pressure will make the volume go back to normal, or go from normal to full. This could be with my finger on a capacitor, a tweezer tip on just the bare board (no metal contact), or sometimes just slightly rotating the whole thing. The signal never cuts in and out, it just goes from set volume to full volume.

I'm starting to go crazy! Anybody have any idea what I could check next? Thanks in advance!

Here's a gutshot for good measure:

[idy]

Sounds like a poor solder joint. You don't show us the solder side. But you can't always see a bad joint. That's one thing you don't mention doing, going over all the solder joints.

[GibsonGM]

Yup...likely bad solder joint on board, pot, jack or switch.  Please don't use metal tweezers to push around on a board, lol...a wooden chopstick type thing is better, won't short things out...

[duck_arse]

one of those jacks has no ground wire. we have no circuit diagram.

[bluebunny]

Try this one:

[bird]

Thanks for the help. Here's a pic of the solder side. Hard to get a pic that shows under the pots, but I don't see anything problematic. I'll try reflowing a solder joints later today. Would a bad solder joint cause a volume surge? I would expect that to cut the signal out, not make it full volume. And could that happen after months of using it?



If the pedal is experiencing the volume jump, the slightest move can make the volume go back to normal, even just barely touching anything anywhere on the components or controls. Is it possible a fault volume pot could make the volume jump? Since the issue started when engaging the circuit with the 3PDT, maybe that mechanical click made something move elsewhere in the pedal?

one of those jacks has no ground wire

The jack without the ground wire is grounded through the enclosure, I tested for continuity.

Could a bad capacitor somehow cause a volume jump?

[FiveseveN]

Would a bad solder joint cause a volume surge?

Absolutely, if it's on the pin that goes to ground.

The jack without the ground wire is grounded through the enclosure

Yeah, don't do that.

[idy]

And yes, a bad solder joint may act up after months or years.

[GibsonGM]

The 'surge' may be happening when it's been moved enough to make good contact for a second...that may be the REAL level the pedal is supposed to put out.  The dodgy solder could be making such poor connection, it's like a resistor instead of a direct connection. 
You might find the culprit by "Chop sticking".

[bird]

Well, I reflowed the whole ground path and as many other places as I could reach. Tested it unboxed, it worked, boxed it up, still worked! I guess the real test will be the next band practice.

So I guess it was probably a bad solder joint. Thanks for the suggestions and explanations! Learn something new everyday. Thanks!