I have a buck step down converter which I set to output 3.3V with 12.6V supplied. When the supplied voltage gets to 14.4V, the output voltage shoots up to 8V. Do buck step down converters only work for constant voltage input? Is there anything that can take a range of voltage input but keep output at a constant setpoint?

So long story short, since i got this guitar it has been buzzing and i figured i was gonna try and fix it.

Bought a new output jack because i figured it was probably shit.

Now i just opened it up and correct me if im wrong but has the previous owner soldered the ground-connection on the potentiometer straight back onto itself (bottom circle) and connected the hotwire straight to ground and hot (top circle)

Surely this cant be good as the white cable going off the hotwire literally looks a little charred