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Pickup selector switch not completely working?

Discussion in 'Pickups & Electronics [BG]' started by Snoa, Nov 2, 2013.

  1. Snoa


    Jan 17, 2011
    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.
  2. JTE

    JTE Supporting Member

    Mar 12, 2008
    Central Illinois, USA
    Start with real troubleshooting. Get a small ferrous metal screwdriver. Tap each pickup in each switch position. If you hear a mettalic thud when you tap the bridge PUP it's working. If this test confirms your suspicions, then look at the wiring.

    Look at the wiring carefully and see if there are any stray strands of wire shorting any of the switch lugs.

    If the tap test shows the switch is working correctly, then look at balancing the levels by bringing the bridge PUP closer to the strings.

  3. Snoa


    Jan 17, 2011
    D'oh. Can't believe I didn't think of tapping it with a screw driver. Well, after doing that, it seems that the bridge pickup still comes in on the middle position, but is EXTREMELY faint, while the neck pickup doesn't seem to get fainter at all in the middle position, if it does then it's hardly noticeable. Checked the wires, nothing was really in the way but I still moved some suspect-looking wires just to be safe, still no go. The bridge pickup is already higher than the neck pickup, should I still move it up even more? I feel like if I did move it up enough to balance it out in the middle position, then it would get REALLY loud when I flipped the switch to the bridge pickup, since it does seem to actually decrease the volume quite a bit. And I did try fiddling with the knobs to try and see if I could make just the bridge pickup come in more, but nothing worked. I mean, I could turn up the treble to make the pickup come in louder (since the bridge pickup has a more treble sound to it), but that also added treble to the neck pickup too so it didn't really balance it out.

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