Wah Pedal Blowing Up

I have a Budda Wah I got off of Ebay.



Either with the battery or powersupply, it does not "wah", it just has a minor volume change.



So I open it up and there is a bad solder job on one of the resistors ... I replace the resistor. It works for about a minute and the "wah" works great! Then it blows up again and back to the volume effect. I replace the resistor again, it works for a minute, then blows up.



Any idea what I should look at next? Could the value of the resistor be off?



Thanks!

Wah Pedal Blowing Up