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Pickup Failure in '68 P-Bass

Discussion in 'Pickups & Electronics [BG]' started by jmlee, Aug 24, 2012.


  1. jmlee

    jmlee Catgut? Not funny. Supporting Member

    Jun 16, 2005
    Halifax, Nova Scotia
    Oh, dear...last week I was heading out to a blues job that I intended to play on upright. I thought I'd bring an electric along just in case anything went wrong or if the feedback ate me for dinner. I went to the rack and pulled out my trusty '68 P-Bass (which was my main instrument for decades). Because I had a Raven Labs PBR-1 pre-amp in it and hadn't played it for a while, I though I'd better check the batteries. Plugged it in and not a whisper. Crap! No time to take off the whole pickguard and change the two 3V cells--even if I could find any around the house. Took my Jazz and headed off.

    Well, tonight I decided to change the batteries. I took everything apart, replaced the cells (which interestingly read 3 V each--old *and* new--on my multimeter). Put everything back together. Nada. Took it apart again. Systematically checked the pre-amp and its switching output jack. All good. The only explanation was no signal from the pickups. Uh-oh. Desoldered the pickup leads, multimeter gives me open circuit. Uh-oh. Took off the strings, unscrewed the pickups and checked their resistance. 5.4 kOhms on the neck pickup. Nuttin' on the bridge pickup. (I mean the two halves of the P-Bass split pickup system here...) Desoldered the bridge pickup. Open circuit.

    So, after 44 years I have an open circuit on one pickup. I *hate* to replace those pickups after all we've been through together. (Maybe I shouldn't be so sentimental. The bridge corroded away and I put a BadAss II on--and I did put the pre-amp in...) But...

    Anyone have any idea whether pickup repair is possible? Or should I just get shopping?

    Thanks as ever.
     
  2. zuma

    zuma

    Dec 21, 2006
    East Los Angeles
    #1...I think we should put Data on this one.
     
  3. mech

    mech Supporting Member

    Jun 20, 2008
    Meridian, MS, USA
    IME, there are two most likely modes of failure for this type of PU...

    1) A solder joint gone bad where the coil wires are soldered to the leads at the eyelet. The insulation on the coil wire is melted/burned off by the heat of the soldering process and remains as a contaminant around the copper wire. Try reheating and adding just a taste of new solder tinned onto the end of the tip of the iron so good reflow will occur. Use a smallish tip but one that will hold some heat. Be quick but be sure all the old solder reflows.

    2) One of the coil wires has broken right where it joins the eyelet, probably due to expansion of the bobbin material and the coil wire being a taste brittle due to the original soldering process. I have repaired this type of failure by gently scraping the insulation off the coil wire to expose the copper and creating a small solder bridge between the coil wire and the eyelet. I have found that a small pocket knife blade or dull X-acto blade are better for this purpose since a truly sharp blade can easily cut the wire. It's a delicate process and not always successful but I know of two such repairs out of three I've done that have lasted for over 10 years.

    If the start wire from the inside of the coil is broken, the solder bridge is the only hope of repair I know of. If the finish wire on the outside of the coil is broken, one turn can sometimes be gently unwrapped and a new connection made.

    It is possible that the wire has opened on the inside of the coil but I've always had a hard time understanding how that would happen unless the wire is wound directly onto the magnets and one of the magnets moves and breaks the wire.

    If the above repairs can't be made or don't work you may want to use a reputable rewinding service for both sections to retain as much originality as possible. I'm sure there will be others along to give recommendations of who to use. Best of luck with your old friend.

    mech
     
  4. jmlee

    jmlee Catgut? Not funny. Supporting Member

    Jun 16, 2005
    Halifax, Nova Scotia
    Thanks so much. Just the sort of experienced and useful advice I've come to admire on TalkBass. This place restores one's faith in human nature.

    I've had a very close look (with a magnifier) at the exposed wires leading to and from the coil through to the solder points on the top and bottom of the pickup. The wire seems entirely intact. I re-touched the four solder points with a lightly tinned iron in case of a break there. No glory. Whatever the problem, I'm inclined to think it's internal to the coil. Like you, I have no clear idea how that could have happened. It's hard to imagine it being either mechanical or corrosive (I teach engineering in my day job), but there you are.

    Oh well, c'est la vie. There's no magic in '68 Fender P-bass pickups I suppose. I'm going to just move on to replacing the set with something vintage-sounding. Perhaps Seymour Duncan Antiquity IIs. Or maybe I'll go crazy and put a couple of Lindy Fralin's pickups in. Best cogitate on that a bit...
     
  5. Lo-E

    Lo-E

    Dec 19, 2009
    Brooklyn, NY
    Since you already know about Lindy, I'll suggest this:
    Send it to Lindy. If it's repairable, he'll repair it. If it's not, he'll rewind it. In either case, he'll make it as close to the original spec as possible.
    Lindy's a very honest guy and his prices are very reasonable - $65USD last time I had one done.

    He's not really big on email, so it's best to call him. I'd recommend calling when you have some free time as the man likes to talk. He can be a little hard to get off the phone! :)

    EDIT: Oh, I forgot to mention; Mech's assessment is 100% right on the money!
     
  6. walterw

    walterw Supportive Fender Gold Supporting Member Commercial User

    Feb 20, 2009
    alpha-music.com
    +2, mech's got it exactly right.

    (and +1 to lindy being the man, but a bit of a technophobe; not much email, and no credit cards or paypal! you gotta send him an actual paper check in the actual U.S. mail, like an unfrozen caveman!)
     
  7. wraub

    wraub

    Apr 9, 2004
    ennui, az
    deviated prevert
    .
     
  8. wraub

    wraub

    Apr 9, 2004
    ennui, az
    deviated prevert
    I find this refreshing.

    wraub
     
  9. +1 to sending it in to someone - I'd try to think of this type failure as an excuse to rebuild it.

    Good luck / keep us posted...
     

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