Help troubleshooting DIY Plexi-drive

[John Nada]

Hey guys,

I've build a plexi style overdrive (The Plexi, from Das Musikding, built documents are over here: https://www.musikding.de/The-Plexi-Overdrive-kit) last year as a present for my girlfriend. It worked great for months, but the last couple of weeks it has a huge bump in volume when engaged. At first the level pot was at 12 o'clock to match, now it has to be turned down to a bit below 9 o'clock. Ofcourse I tested this with different power supplies, amps, guitars, cables etc.

I'm still pretty new to this though, I haven't build many pedals. This was the first one and I was lucky enough to have it working on my first try. The only thing I changed compared to the original design, is that I swapped the 47pF for a 470pF at C3. I did a bit of audio-probing and I hear an increase in volume from one side of C3 to the other, but it's normal again at C4.

I'm not sure where to look or what to check in order to tackle this problem. I friend told me the description of the issue sounded like a bad solder joint in the diode. If you guys can guide me along what to check, that would be great! The PCB is glued to the chassis with some 'legs' that came with it, it sticks on there really well, so I didn't rip it out yet in case it's not even necessary. The only thing weird I've noticed is that the diode runs 12.48v on one side and 0 on the other. But I'm a beginner, so still figuring this all out.

Cheers,

John Nada

[antonis]

the diode runs 12.48v on one side and 0 on the other

Your PS is 12VDC or 24VAC (both nominal..)

[bartimaeus]

If your friend suspects that it's a bad solder joint, then you should probably take out the board, look over all the solder joints, and maybe even reflow all of them to be safe.

That said, in my experience Plexidrives has a lot of volume on tap. Maybe it was working wrong all those months, and is finally working correctly. If everything sounds the same but you just have more volume available, that seems like a bonus to me?

[John Nada]

If your friend suspects that it's a bad solder joint, then you should probably take out the board, look over all the solder joints, and maybe even reflow all of them to be safe.

That said, in my experience Plexidrives has a lot of volume on tap. Maybe it was working wrong all those months, and is finally working correctly. If everything sounds the same but you just have more volume available, that seems like a bonus to me?

Well to be clear: he suspected that based on my story, not by looking at the pedal.

I use a Xotic SL Drive and Electric Majik Albion myself, they both have a unity volume with the level halfway open. The Plexi Drive I made for her used to be the same. Personally I never switch a pedal like that off, just roll the volume back, but she likes to turn it off for cleaner tones.

But I have to admit, with the level just beneath a quarter it is already a bit more than unity level with the amp. The downside is, that the pedal sounds a bit more fuzzy and muddy, unless you turn the level halfway. But at that point, it is three times as loud as your amp is set.

Regarding the 12v, I found out that was just a mistake on my part. My 9 volt adapter and the adapter of my power supply got mixed up, very stupid, very beginner. When you have too much stuff, it sometimes starts to look alike I guess.