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Corroded pots on my friends bass. Has anyone seen anything like this before?

Discussion in 'Pickups & Electronics [BG]' started by matthew packman, Mar 3, 2016.


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  1. matthew packman

    matthew packman

    Jan 15, 2016
    I guess I can't get a picture on here but it's a white, gray film covering the pots entirely. There is no sound and the wiring looks complete. Any definite answers would be greatly appreciated. I'll try and get a pic soon.
     
  2. Are you near the ocean?
     
  3. matthew packman

    matthew packman

    Jan 15, 2016
    the bass is a 1968 kustom bass, not sure where it's been along its lifetime but it's in South Dakota now. It is a semi hollow body though.
     
  4. Eastern South Dakota? How long has it been there? There's a lot of salt on the roads for about 9 months of the year and high humidity at times.
     
    matthew packman likes this.
  5. This is what I pulled out of a 1992-ish Gibson ES135.

    9ae302aa.

    635cc457.

    Moist air can do such a thing (especially since it's a semi-hollow, thus air can move freely in the instrument), but maybe it could be galvanic corrosion?
     
    matthew packman likes this.
  6. Jazz Ad

    Jazz Ad Mi la ré sol

    Typical of instruments stored in basements.
     
  7. It sounds to me like the pots were plated with cadmium and that it has started to oxidize and deteriorate. I've collected and restored vintage tube stereo for quite a few years and this is common in that type of equipment. The resulting dust is toxic if inhaled. I'm not sure exactly how toxic, but something to avoid for sure. So don't use a wire brush on it.

    I usually spray a mix of isopropyl alcohol and water, or some type of spray cleaner with "Oxy", onto a paper towel and wipe it off.

    There could be numerous causes of "no sound" and, most likely, it is not related to the cadmium.

    First step would be to spray contact cleaner into the pots - there is usually a gap where the connection tabs emerge - and turn them back and forth a bunch. Pots are often intermittent but will usually pass some sound even when quite dirty. The problem is more likely to be a bad solder joint.

    If you still have no sound, you should measure the resistance of the pickup(s) to make sure you don't have a break in the coil winding.

    I'm guessing access will be your biggest problem since it's a semi-hollow design. How do you get in there to test / remove / replace parts???
     
    matthew packman and kjones like this.
  8. Growlmonkee

    Growlmonkee

    Jan 30, 2013
    Florida, U.S.
    If you want to get it working yourself, quality pots are around $5 each, I wouldn't bother with any that are badly corroded. First thing to do would be measure resistance across the pickup leads, after removing them from the controls, just to make sure the pickups are good, they should read generally between 6k and 13k ohms, (generally), that would let you know if they have broken coil wires, or not. If the pickups are good, it would not cost much to rewire with new pots, provided you can solder. The hardest part would be getting in through the pickup holes, a lot of it could be soldered outside the bass.
     
  9. matthew packman

    matthew packman

    Jan 15, 2016
    Thanks for info. The pots are on the back of the pick guard so that's easy to get to. You would have to go through the presumed pick up holes for to get at the those wires. The bass resembles a rickenbacher body style.
     
  10. matthew packman

    matthew packman

    Jan 15, 2016
    It looks exactly like the top picture
     
  11. matthew packman

    matthew packman

    Jan 15, 2016
    By lead do you mean pick up to pot?
     
  12. matthew packman

    matthew packman

    Jan 15, 2016
    Yes eastern sd
     
  13. Growlmonkee

    Growlmonkee

    Jan 30, 2013
    Florida, U.S.
    yes, I meant both the wires from the pickups, taken off the pots, if you put an ohm meter across the 2 "leads" wires, it should read around between 6k, and 13k ohms resistance, if it does , the pickups are ready to go, most likely, if they are dual coil, they may read more than that, if they read a ton less, they are probably shorted, if you get no reading they are probably open, either would be bad, if the wires coming off the pickup are intact. If the pickups work, those pots are not really a big deal to change, looking at the rust and corrosion, and the fact that they don't cost a lot new...I'd change them to new, and not clean them up, if I knew the pickups were in good order, and would surely change the jack to new one too, we're talking around $25 for good quality parts, and a couple of feet of new wire, vintage value is great, but not when the stuff is ruined, those pots are ruined.
     

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