Hello.
I never burnt anything since I build pedal, but today I was wiring into the box a Triple Wreck on stripboard. It worked out of the box.
I just forgot to wire the input and the output wires from the board to the footswitch, while the board is into the box still open. So during the test I got no sound when the board was engaged. After some seconds I saw a wisp of smoke from the box and I disconnected the PSU. I didn't notice anything burnt, no parts was hot. I found the input and output not soldered on the footswitch, as I said, and honestly a little mistake: a wrong position of the 9v wire on the board, but it just bypassed the 47R resistor, seeing the layout the 9v in the end was going exactly where had to go.
After connected all the wires I noticed that the Volume pot had a brief rotation.
I tested the pedal and the circuit works, now. But I know the Volume pot have something wrong. I forced the rotation and now it seems unblocked and it rotates well. Probably I'll replace it, and I'll check with the multimeter if it's really ok.
But I'm wondering what was that smoke and what suddenly happen to the Volume pot?
Reminds me of a time I was trying to search for info on a potentiometer that heated to the point of glowing while emitting smoke. Truly a sight to see.
However, my google search of "lighting up and smoking pot" returned less relevant results. ;D
A pot is a resistor, so it has a wattage rating. If you exceed that, you will let the magic smoke out.
Oh yeah, it's quite exhilarating until the smell hits you.
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Chances are you've sent 9v straight through the pot. I did that once, missing a cut in the vero layout.
The board is working, because I tested it before the wiring.
I suspect an accidental contact during the test into the box. I admit that the test was a bit clumsy: I had two flying 1k resistor coming from the positive of the DC jack (that was for two leds for two other boards still out of the box). Maybe one of the resistor touched the pot? This means that the 9v gone through the 1k on the body of the pot, and the box was grounded. So: 9v -> 1k -> ground. The Volume pot was set to zero. Is it important? ???
I am not sure what was that smoke, because I couldn't see anything evident burnt. I just found that the pot was partially stucked. After I forced that pot I tested the whole thing and it seems to work fine.
I guess I heard a mechanical click noise while I rotated the pot. And during the test it was maybe a bit scratchy passing when spot where it was stucked, sometime.
Sounds like the resistive track in the pot burned, and possibly the wiper as well, right at the spot where the wiper was touching. Why don't you pull the pot out and replace it? Then take the pot apart and examine the damage. Be sure to post a pic of it here for us.
Everything seems ok, now. But later I'll replace that pot.