Changing pickup magnet polarity (undoing RW/RP)

Discussion in 'Luthier's Guitar & Bass Technical Discussion' started by suhr_rodney, Jun 12, 2006.

  1. suhr_rodney

    suhr_rodney Supporting Member

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    I was ordering some parts from StewMac over the weekend and noticed they give instructions for changing the magnetic polarity on single coil pickups. I've done it before with humbuckers where you can simply flip the magnets, but never with single coils. I have a couple of spare middle pickups (RW/RP) due to the recent acquisition of a Suhr BPSSC. If I can change the magnetic polarity and reverse the wiring, then I can use these pickups in my next guitar. I went ahead and ordered the supplies as they were pretty cheap. Just wondering if anyone has any experiences they can share. Anything I should know before I dive in?
     
  2. suhr_rodney

    suhr_rodney Supporting Member

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  3. Mark Robinson

    Mark Robinson Member

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    A humbucker has the magnet beneath the coil, with screws or studs, sticking through a bobbin, which in turn has an interior wall.

    A Strat or Tele, has magnetized polepieces, pressed into fiberboard or similar material top and bottom, with no lining or interior wall between the polepieces and the wire. So though you might be able to extract individual polepieces, getting them pressed back in, without shredding the interior coil wire, would be nearly impossible.

    An alternate tactic would be to de-magnetize and re-magnetize the pickup as an assembly. The equipment to do that would certainly be more costly than several replacement pickups.

    From my point of view, there is no low capital/low cost way to re-orient the magnetic field of a single coil. But I'm pretty sure, Seymour Duncan could handle it, or any number of pickup makers who get into the magnetic side of that business. Good luck with your project!
     
  4. John Phillips

    John Phillips Member

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    You can do it extremely easily IF it's a modern Fender US Strat-style pickup with a plastic bobbin - the magnets are held in separate tubes and are not touching the coil, and actually slide out quite easily.

    But you CANNOT do it on a vintage-construction pickup - as Mark said, you'll wreck the coil. The only way to reverse the polarity on one of these is to remagnetise it.
     
  5. has-sound

    has-sound Member

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    This works with Alnico V magnets. Use a vise or make a C-shaped fixture from wood and epoxy two small round neodymium magnets about an inch apart. Orient the magnets so that they pull toward each other, and identify the north/south polarity. Move the pickup as slowly as you can between the magnets with the north pole of the pickup facing the south pole of the magnet. Don't let the pole piece touch the round magnet while doing this. Several passes through the magnets does the job. It takes a very steady hand! I have a little wooden jig that holds the pickup and keeps the poles from touching the charging magnets. I just slide it between the magnets while they are attached to a small table vise.

    -Stan
     
  6. illinimax

    illinimax Gold Supporting Member

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    I've done this. Worked fine.
     
  7. suhr_rodney

    suhr_rodney Supporting Member

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    This sounds like the process that StewMac described and the one which I am trying to mimic. I ordered and received the magnets, polarity tester and small vice from them. Before getting started I have a couple of questions. 1.) Does it really matter if the pickup touches the magnet? (No permanent damage, I assume) 2.) Is it feasible to use a small non-metallic barrier on each side of the pickup to keep it from physically touching the magnet? 3.) Short of buying a gauss meter, is there a way I can tell when I've made enough passes between the magnets?
     
  8. has-sound

    has-sound Member

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    1) There wont be any permanent damage 2)I made a wooden holder that isolates the poles from the magnet 3)I usually do 3 or 4 slow passes and have been happy with the results.

    I would like to get a gauss meter but they are very expensive. Not selling enough pickups...yet.

    -Stan
     
  9. Jason Lollar

    Jason Lollar Member

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    I can tell you, having a gaussmeter myself, that if your using those neo disks about 1/4" X 1/4" that they wont fully charge a typical length alnico 5 slug. It has enough to reverse the polarity but will only charge to about 1/2 the capacity the rod has.

    You also have to flip the lead wires which depnding on the design of pickup and who made it you may have to flip the leads at the pickup rather than at the volume pot or switch.
    If you flip the leads on a fender style at the pickup there is a small chance of breaking the coil wire which may or may not be able to be repaired depending on if its the inside or outside of the coil and how far back it breaks.

    The kind of gaussmeter you need IMO if you are going to make alot of pickups and really get into designing them is about $400 and they go higher
     
  10. has-sound

    has-sound Member

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    Hi Jason, how have you been? I am using the Stew Mac 1" neo disks. Do they fare any better?

    What is the "normal" gauss of say an A5 Strat slug?

    -Stan
     
  11. Jason Lollar

    Jason Lollar Member

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    a 1/2" by 1/2" will charge them up to full potential which on my meters would be 1200 gauss max. Not everyones meters are calibrated the same or they take the measurements differently than i do.

    i dont know about what you could get at stew mac.
     
  12. alderbody

    alderbody Member

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    ...These pickups you have are RW/RP in regard to the other pickups of the same set, right?

    If all the RW/RP pu's you have are the same polarity/orientation etc to each other, why all this trouble to change them?

    I mean, you'll make a new guitar with a e.g. "South" magnet orientation instead of the "North" your other guitars might have. So what?...


    OK, this argument is valid only if your spare pickups were of the same spec, but have you tested them in case they really are?

    just a thought... ;)
     
  13. suhr_rodney

    suhr_rodney Supporting Member

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    Great question and worth asking. You are correct. My immediate goal is to reverse the magnetic and electrical polarity of ONE of the two pickups so that the middle pickup with be RWRP with respect to the bridge and middle pickups. However, I will eventuall buy more BPSSC systems and I would love to be able to change the polarity of the middle pickups so I don't have to replace them on every guitar I put a BPSSC system on.
     

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