Sparks & Burning Pot!

[maurice]

I've just completed a Vico Vibe (http://www.diystompboxes.com/smfforum/index.php?topic=97698.msg852351#msg852351) and placed it into an enclosure.

It was  powered by a 9v battery and playing through my amp then after a few mins, a glow came from the sensitivty pot followed by sparks.

Luckily I had the back off the enclosure and could isolate the burning, but what on earth could cause this?

[CynicalMan]

Usually that happens when there's 9V power across one side and the wiper of the pot. With a constant voltage, power is inversely proportional to resistance. This means that as the resistance of the pot goes down, the power dissipated goes up. You probably had the sensitivity set to one side and the pot was dissipating a lot of power.

On that vero, pin 1 of the pot is connected to 9V. So the wiper (pin 2) probably shorted to ground.

[maurice]

oh... any ideas how I could avoid it?

[Mike Burgundy]

Find the short, make sure it doesn't happen again. There's definitely a connection somewhere where it shouldn't be. Perhaps a wiring error, perhaps it's shorting to the enclosure.
The battery is probably getting very hot with this too, trying to supply all that current.

[maurice]

Thanks, I imagine its shorting on the enclosure. Should I replace the pot too?

[Jdansti]

oh... any ideas how I could avoid it?

+1 with Mike.

Glad you're building pedals!  Please accept the following as constructive criticism and not a personal attack. 

The way to avoid it is (1) to not make the wiring/soldering mistake, or (2) find the problem and correct it. I looked at your previous photos and it appears that you are still learning to solder.  That's OK.  Just take the friendly advice that folks are giving you and continue to improve.  Please see this great video on soldering:

Do the photos in your other thread represent the condition of the board when it fried or did you correct the solder problems?  If not, we would need to see new photos. Please include a photo that shows the off board  components and a picture of the vero layout you used.

[maurice]

Thanks, all advise is greatly appreciated. The soldering on my final board was waaaaay cleaner than those in the pics but yes I'm still new to soldering and pedal building.

Just removed it from the enclosure and tried it again but the effect no longer works. I'm guessing the pot fried so I'm gonna replace it and see what happens when tested outside a case

[Mike Burgundy]

Do you have a DMM (digital multimeter)?
With that you can test the pot (which, considering the magic smoke^* was let out should be replaced anyway) and trace shorts easily. If you don't have one, I strongly recommend getting one. Idespensable tool.

*all electronics may stop functioning if for whatever reason smoke comes out. Therefore one can deduce all electronics contain magic smoke, which makes it work, and one should take care to contain the magic smoke inside electronic components to retain their functionality. ;P