SOLVED Weird oscillation with Aion VH Drive channel

[hereonmars]

Hi all,

I built this Aion VH Drive channel pedal (on the left in the video). It sounded great when I first built it and boxed it. I took the circuit out so my son could decorate the enclosure. When I reboxed it, it makes this weird oscillating sound when engaged. I am guessing maybe I knocked something loose, but thought I would post this video and see if anyone has run into something similar and might know a good place to start. With the back off and having it engaged, I noticed when poking around with my finger that IC4 was kinda warm to the touch- warmer than I expected but not necessarily alarming.

Any suggestions are appreciated. I can't wait to get this thing back and running so I can play early 90s death metal riffs.

video with the noise:

schematic: https://aionfx.com/app/files/docs/vh_drive_channel_documentation.pdf
gutshot:

 

[DailyDovetails]

Try moving the input and output wires away from each other. Ideally away from the ICs also

 

[hereonmars]

Try moving the input and output wires away from each other. Ideally away from the ICs also

thank you! I will give that a shot.

 

[hereonmars]

Try moving the input and output wires away from each other. Ideally away from the ICs also

went in, reflowed all the solder, made sure there was more space between input and output wires. When unboxed, the pedal sounded like it's supposed to. I thought it was fixed. I box it back up and I get this:

Any idea why that would be? I noticed again when poking and prodding around that IC4 was very hot. Should I start measuring voltages, or is there a couple points where I could check the signal with an audio probe to rule out the place where the problem is happening?

 

[zgrav]

are any of your pots under stress when positioned in the enclosure? try loosening the nuts on all of them by a small bit and see if you get a different outcome when it is engaged.

 

[hereonmars]

are any of your pots under stress when positioned in the enclosure? try loosening the nuts on all of them by a small bit and see if you get a different outcome when it is engaged.

that was it! It got better when I completely loosened the nuts. Any tightening on them whatsover and the sound cuts out. Should I tighten to a normal tightness and reflow the solder on the pots maybe?

edit: tried that, same result. Any tightening of the nuts on the pots whatsoever causes the issue to come back. Maybe I just need to put the knobs on with the nuts completely loose?

 

[jwin615]

One of two things
Back of the pot is making contact with a solder point-have pot condoms on?
Damaged pot from over tightening.

 

[hereonmars]

I'm pretty sure I do have the condoms on but will double check. Is there any way to check which pot is damaged? I'm guessing measure resistance at the legs and see if it checks out?

 

[Nostradoomus]

Tighten them one by one til it cuts out.

 

[hereonmars]

Thank you to you all. I am thrilled to report this issue is solved.

I had covers/condoms/jimmy hats on the back of the pots, but the profile of those covers was way too high and left a good couple mm of empty space between the backs of the pots and the flat part of the cover. I trimmed it and re-stuck them on. To be safe, I took a small piece of 1/8" thick eva foam behind them to make sure nothing was being stupid. after putting it all back together and even tightening the nuts on the pots, the issue is gone. Not sure WHAT was shorting WHERE, but at this point I don't care any longer.

I greatly appreciate the help