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SCN bridge pup repair

Discussion in 'Just Pickups' started by tklaavo, Nov 26, 2012.

  1. tklaavo

    tklaavo Tele-Holic

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    Hi,
    I have a set of Fender Samarium Cobalt Noiseless Tele pickups. While soldering, I made something stupid and the bridge pickup went dead. I'm pretty sure the coil is just broken somewhere. No sound, no resistance value.

    I have been examining it, looks very complicated and delicate design. I have means to rewind, but I have no idea of the specs. I think I have figured out the construction and how the coils are connected.

    Does anyone know the specs of the original? Wire gauge? Number of winds?

    If anyone has one of these, I'd be happy if I could get a reference DC resistance value to get an idea what to aim for. There's nothing to lose anymore, so I might give it a try.
     
  2. Teleterr

    Teleterr Friend of Leo's

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    Can you see the coil wire where it comes out to the post where it and the leads are soldered together ? Its smaller gauge than normal , so even if you don't wear glasses, reading glasses might be helpful.
     
  3. tklaavo

    tklaavo Tele-Holic

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    Hi,
    I'm pretty sure the start of the wire is broken at the eyelet at least. Here's some pics to clarify what I think. I might be wrong, so if someone knows better of this construction, please correct me!

    [​IMG]

    In the pic above, the leftmost solder point is the end of the upper coil, it is jumpered there. The middle is grounding for the bridge screws. The one in the right is where the lower coil should start, but I can't see any copper wire there. I guess my soldering iron was too hot when I was re-attaching the leads and caused some harm. Or I was soldering in the wrong spot, maybe. It was last winter.. can't remember all mistakes so clearly.

    By the way, I have removed the coil tapes to examine the damage, and that might have broken the wire more.. but it was dead already then.

    This is the bass side:

    [​IMG]

    There's a piece of metal, where the upper and lower coil wires meet. They both seem to be there still.

    The treble side:

    [​IMG]

    A similar soldering spot, where the upper coil ends and is connected to the eyelet with an unisolated jumper wire.

    The lower coil could be metered for DC resistance from the start eyelet and the connecting point on the bass side. It's broken, no reading.

    If the upper coil was fine, I should get a reading when metering from both ends, but there's none. So the upper coil is dead too. Interesting.

    Another interesting fact: both the top and bottom of the pole pieces are magentic north. The south is between the coils, and the north needle of my compass points there, on the long sides of the pickup. Kind of a figure-of-eight magentic field.

    I could just cut the wire out and rewind with 43 AWG, I have plenty of that. There's no way to make this work as it is. The wire looks very thin, it might be even thinner than 43.
     
  4. Teleterr

    Teleterr Friend of Leo's

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    I have 2 dead stacks too,and its the top coil just like yours. I think thats the Lawrence design. The bottom coil senses little or nothing from the string, since there s no disturbance to the field. It does get hum, and is out of phase to cancel it, leaving a clean signal from the top. From what I've read, the coils can be different and still cancel noise well, but for the best result rewind both. Yeah, its smaller than 43 gauge in diameter.
     
  5. GCKelloch

    GCKelloch Tele-Afflicted

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    I think it's 44g wire. It won't sound the same with 43 because the coil dimension is crucial to the phase coherency of the design. It's probably burnt at the eyelets. Maybe you can unravel a wind and resolder?

    Otherwise, see about replacing the bridge pickup with a very affordable Wilde NF L290SL, or L298SL. I think the L298SL is the closest match.
     
  6. Teleterr

    Teleterr Friend of Leo's

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    I just looked up the source writing of the hum canceling for unequal coils. 43 vs 44 is 11% bigger so the turns in the coil go down by the square of the difference = 23%. 20db is not bad for hum canceling, but you need 18% difference for that, So rewind both for good noise reduction.
     
  7. tklaavo

    tklaavo Tele-Holic

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    Thanks for the comments. Both coils are broken so I need to rewind it all. Gonna be tricky with such small coils etc. I don't mind using wrong gauge, there's no way to make this as original. It's gonna be an experiment and if it sounds fine enough, it will have a place in some future guitar. The neck pu from the set already has a nice life with a bridge humbucker. When I have the time I'll just wind a good amount of 43 and hope for the best.
     
  8. tklaavo

    tklaavo Tele-Holic

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    Did it.

    I rewound both coils with 43 AWG wire using my low tech sewing machine winder. In the bottom coil I put about 4600 winds and on the top 5100. The hardest part was to cut the old wire, as the coils are so low, no cutters fit between the plates.
    It now has a dc resistance of exactly 10kOhms. Somewhere I read the original is around 13k but if it's 44 gauge wire, the total number of winds should be about the same.
    It works, sounds pretty much like a Tele should and is noiseless. Quite bright, but not in a bad way. Probably the thinner wire would make a less bright tone. It has a new life, and will go into one of my builds-in-process.
    I'd like to pair it with a neck humbucker, but there would be big difference in brightness, maybe some custom wiring will be needed.
     
  9. GCKelloch

    GCKelloch Tele-Afflicted

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    Exceptional! I'm surprised it worked. Not surprised it's brighter. Probably more like a typical Fender sound. What you lost was the coil phase-alignment, which is only achieved if everything is calculated as a specific formula. The original ~2006 SCN's were optimally even and clear. Some thought they were dull because they weren't as bright as Fenders, but the clarity was actually better.
     
    Last edited: Dec 12, 2012
  10. Teleterr

    Teleterr Friend of Leo's

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    Cheers. Glad it worked out. Its always nice to hear how things ended up.
     
  11. tklaavo

    tklaavo Tele-Holic

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    Hi,
    I'm interested in what this means, could you explain a bit more about the coil phase alignment?

    I'm quite new to pickup theories.. I know the basic principles, like how the wire gauge and coil size / shape make a difference and how the magnet strength and placement (and material inside the coil) can alter the sound. But this stacked coil design is all mystery to me.

    In this pickup, the coils are RW / RP. I know some have made stacked pickups with just long Alnico poles that go through both coils, and the lower coil is RW but not RP. I guess they work just because the lower coil doesn't sense much of the string (If it did, there should be lot of canceling of the signal)
     
  12. tklaavo

    tklaavo Tele-Holic

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    An update - I wasn't happy with my first rewind, it was too bright and wouldn't work with a neck humbucker I'm planning to use with it. So I did it once more. 43 AWG wire again, now more turns. With more tension I was able to get aobur 5300 on the bottom and 6500 on the top coil. Now it's closer to a typical tele bridge pup tone. Quite loud output! I'm probably still going to wire the tone control to bridge only so it can be balanced with the darker neck HB.

    The guitar is still in the works, I'll post more when it's done before spring (I hope)
     
  13. Teleterr

    Teleterr Friend of Leo's

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    Thanks for the update. Have you ever compared 2 p/ups that had the same number of winds but different winding tension ? The coil will be smaller w more tension, but not by too much. I just wondered if you can hear the effect of coil tension as a factor. I've made low impedance pickups literally winding them by hand, or by a hand powered winder, so they have little tension. They have a sound quality that I attribute to that lesser tension. DiMarzio p/ups to my ears all have a similar sound. Since they all have different magnets , shapes, and number of turns, I think maybe DiMarzio uses more tension than other winders.
     
  14. Rob DiStefano

    Rob DiStefano Doctor of Teleocity Vendor Member

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    pack in as much turn count as possible, that's key in lessening the shrill treble and augmenting the midrange. be careful with wind tension - too much will cause shorts and too little will greatly lessen the max turn count.
     
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