Distortion III - suddenly very loud

[Bret608]

I have a Distortion III I built in 2019 and I love it, but recently replaced the board-mounted stereo jacks with some Lumberg, just wired in per the switching board BOM. They had a habit of coming ungrounded, and relying on the ground wire to the footswitch lock washer didn't help since it comes loose easily so would also cause issues.

So that worked and I've been good for a couple of months. Now though, the pedal is suddenly super loud, as if the volume knob is dimed all the time. You can hear it make some small change in sound but essentially it's like it's being bypassed. I can get it into bearable territory if I have both hard and soft clipping fully on. Also, the gain pot will rein it in if I roll it back a lot.

I had PPCB build do something similar recently, and this turned out to be a bad pot. So I metered all the pots by clipping my DMM to lugs 1 and 3 and watching the resistance across the sweep. Volume, soft, fat, and filter all seem correct or as expected. I can't make sense of drive--it never reads higher than 60k at any point in the sweep, then goes down to 1k or so (probably due that adjacent 1k resistor). Is that normal since it's in circuit and neither side goes to ground? The hard pot also reads oddly, seemingly just 64k across the whole thing, but wondering if that's to do with the taper and/or how it's situated in the circuit.

Not sure where to turn at this point. Could the switch board also be worth looking at, especially given my recent jack swap?

[jessenator]

That's super weird. I would think it's the volume pot to blame if it's way too loud, but said it read as expected?

How's the continuity between lug 1 (ground) and another ground pad? Could try some safe contact cleaner to see if there's something prematurely bridging lugs 3 and 2?

Probably a crazy thought, but what does R7 measure? That's all I got! Hopefully it's helpful.

[Bret608]

I will check on R7! This pedal is seven years old at this point so you never know. Continuity is good from lug 1 to ground. When the same thing happened on my Carmine build, I thought it was the volume pot but turned out to be the drive. I bet it's the same thing here given the weird reading I got. Will swap them out one at a time when I get back from being out of town shortly here. Thanks as always!

[NorthCoast]

What do you get if you put your Ohm meter between pins 1 and 2 of the volume pot?

[Bret608]

I will check! What would I expect to see there if something's off?

[jessenator]

I will check! What would I expect to see there if something's off?

At full CCW (lowest volume) it should read close to 0 ohms, and then at full CW it should measure close to 100k ohms.

if you turn through the pot's range (slowly) you should see a sweep of ascending values. Malfunctioning pots will have random jumps towards the pot's max value. Might not jump up to 100k, but it'll be higher than it would normally (ideally) plot.

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[Bret608]

Thank you, that helped! All the pots checked out in terms of resistance, even the volume. Then I checked continuity from the pins to ground, adjacent resistors etc. I noticed pin 1 on the volume pot did not have continuity to ground, even though the solder pad did. Magnifying glass showed it needed a reflow and a bit of extra solder. All good now! It must have been a dodgy joint to begin with which got worse when I unboxed to change those jacks.

[jessenator]

Nice work! Glad you didn't have to replace the pot.

[NorthCoast]

Woohoo!