My JS's input jack was worn out (the sound kept cutting out and came back when I jiggled the cable around in the input) so I got a new one and tried putting it in myself. Seemed like a straightforward swap but on the first try I got no sound. I unsoldered the two wires (one white one black) and tried them the other way around, now I get the sound but behind it is the most unholy buzzing and when I move the volume switch there's this scraping noise.

Anyone know what I've done wrong and how I can put it right before I take it into the shop and pay them to do it for me?