Thermionic oscillation issue

[ninemag]

Just finished this build and it’s acting funny... It’s making a feedback/oscillation. More accurately an oscillation that sounds like feedback- when I adjust the gain, tight, and trimmer, they affect the pitch and intensity of the oscillation. Any ideas? Posting pics
Thanks for the help-

 

[Elktronics]

Is this the one with the trim pot to set the low point of the gain?

 

[ninemag]

I believe so

 

[Elktronics]

I built one from aion and had the same issue. I lowered the internal trim pot until it went away

 

[ninemag]

Trim pot lowers it, but it won’t remove it. Did some more troubleshooting- I can hear it when the pedal is off; very low, but I can hear it in the dry signal. And even in the dry signal with no power to the pedal, the gain and tight knobs change the pitch of the oscillation. I’m thinking it’s a growing issue. I double checked my connection a and all appear ok. I trimmed of the excess wire on the i/o jacks visible in the pic.

 

[ninemag]

Hooked it up with no input- footswitch off. High pitch hum still there. I replaced the footswitch and rewired the connections to the board/jacks. No change. Looked under magnification but nothing looks obvious

 

[ninemag]

Went through it again- checked out the trimmer and it looked like it had bent a little and maybe was contacting where it shouldn’t- replaced it. Tested all pots, all normal. Sound is better, but still getting the feedback oscillation. I CAN make it go away when I turn back the “tight” knob, I’d say to roughly 8o’clock. Any higher and it starts getting noisy- the higher set it, the higher the pitch. The trimpot now has no effect on the oscillation

 

[mjh36]

First off, I'm a rookie, 3rd build in, so maybe someone can confirm this. But I thought I read something about the placement of wires next to certain components like the potentiometers can cause issues? I would try running your wires on the other side of the pcb, the bottom plate side, towards the edge of the enclosure away from pots etc. I could be wrong just a thought.

 

[ninemag]

Good idea

 

[mjh36]

Not very pretty, my second build, but thats how I got my wires. I still need to work on my wire length because they act as an antenna apparently.