I have a Villex pickup with the passive mid and treble control in my bass which sounds great when it works. The mid tone control just randomly stops working. I tried using contact cleaner on the pots. I haven't resoldered it yet, but I'm skeptical that would be the problem. Generally when there is bad soldering the signal cuts in and out, but in this case the signal is not interrupted, the tone control just doesn't have any effect. But after a few days, it'll start working again.
Help
Help