So I have an old bass from the 80's, it's stressful trying to diagnose issues with it as far as electronics goes because it's an almost unheard of bass so finding any wiring diagrams are out of the question. So this bass has a pickup selector switch. Top position selects the top pickup, bottom selects the bottom pickup, middle position selects both. Thing is, there seems to be absolutely NO difference in sound between top position and middle position, so it seems like the bottom pickup isn't getting any action when the switch is in the middle position (I should definitely be able to hear it at least a little, the bottom pickup sounds vastly different than the top one). So I checked the wiring (should be noted that I know almost nothing about how basses should be wired) and on the switch there are six total "prongs" to connect wires to, separated into three groups of two (Two for the top, middle, and bottom position each I imagine), for the top and bottom rows, there are two different, thick, cream-colored wires connecting to each one (it looks like they only connect to one of the two prongs for each row, but I could be wrong. Everything was so cramped in there it was hard to tell) and for the middle row there's a thinner, red wire that connects to it; again, it only looks like it's connecting to one of the prongs for that row. I don't know if that's actually helpful or anything, but that's what I see. So what's the dealio here? The bottom pickup definitely works, it just doesn't want to work when the pickup selector switch is in the middle position. Also, there's some hissing that are tied to two specific knobs, the hissing gets louder and quieter when I turn either knob up or down. Is that just bad soldering? (I believe those two particular knobs control treble and low-mids) Edit: It should be noted that there MIGHT be a way to adjust the volume of each pickup, which could be the issue maybe? It's hard for me to figure out what each knob does, and there's 6 knobs total (it has a 4-band EQ) so it's hard to figure out haha.