Dead Magnet

Discussion in 'Just Pickups' started by 61fury, Mar 23, 2016.

  1. 61fury

    61fury Tele-Afflicted

    Posts:
    1,935
    Joined:
    Aug 28, 2009
    Location:
    knoxville, TN
    On a gold foil, can it be re magnetized?. I only noticed because I had it apart and it wouldn't stick to a metal filing cabinet. Who could remagnetize it? Would it be worth it? It did work on the guitar, but it just sounded like crap gold foil1.jpg
     
  2. Rob DiStefano

    Rob DiStefano Doctor of Teleocity Vendor Member

    Age:
    73
    Posts:
    10,033
    Joined:
    Mar 3, 2003
    Location:
    NJ via TX
    easy peasy - just get a really strong magnet (neodymium, rare earth), touch it to ONE side only, and that'll do the trick inside of 5 seconds.
     
  3. dsutton24

    dsutton24 Doctor of Teleocity Ad Free Member

    Posts:
    10,199
    Joined:
    Dec 29, 2010
    Location:
    Illinois
    If it has been demagnetized, then how did it make any sound in the guitar?
     
  4. Tony Done

    Tony Done Friend of Leo's

    Age:
    74
    Posts:
    4,970
    Joined:
    Dec 3, 2014
    Location:
    Toowoomba, Australia
    ^^^^ Good question.

    Is it ceramic or alnico? I'm just wondering if ceramics can get demagnetised, and whether they could be remagnetised if they did.

    When I need to do it I make up a remagnetiser with a couple of big RE buttons held in the vise with a suitable-sized spacer between them, opposing poles inwards. I then just slide the pickup or magnet through it, using a compass to get the polarity the same way, ie north on the magnet facing south on the remagnetiser.
     
  5. jvin248

    jvin248 Poster Extraordinaire

    Posts:
    7,986
    Joined:
    Apr 18, 2014
    Location:
    Lions & Tigers oh Mi !
    .
    I would have expected that gold foil pickup to have a ceramic magnet (and thus be stable) but they could have been messing with Alnico in those. Someone must have leaned the guitar the pickup came out of against a big speaker or a power transformer.

    Home Depot has a selection of Neo magnets in the hardware section. Or find an old computer hard disk drive to take apart.
    Be careful with them as a pair can really pinch your fingers.

    Fun how those older pickups were all a single coil like a P-90. I have some that were built the same and packaged in a chrome humbucker case.
     
  6. mozzman

    mozzman Tele-Meister

    Posts:
    159
    Joined:
    Nov 2, 2015
    Location:
    NEPA
    I've got a Magnetool 24c, if you mail it to me i will zap it.
     
  7. 61fury

    61fury Tele-Afflicted

    Posts:
    1,935
    Joined:
    Aug 28, 2009
    Location:
    knoxville, TN
    Maybe it had some residual magnet quality, not enough to stick to a metal filing cabinet.

    Of course I'm no magnet expert
     
    Last edited: Mar 23, 2016
  8. 61fury

    61fury Tele-Afflicted

    Posts:
    1,935
    Joined:
    Aug 28, 2009
    Location:
    knoxville, TN
    Hey that sound ideal, thanks
     
  9. mozzman

    mozzman Tele-Meister

    Posts:
    159
    Joined:
    Nov 2, 2015
    Location:
    NEPA
    Have you measured the coil to make sure the resistance is ballpark? It should stick to a metal desk or refrigerator.
     
  10. Deneb

    Deneb Tele-Afflicted Ad Free Member

    Posts:
    1,607
    Joined:
    Feb 16, 2011
    Location:
    Ukraine, Dnipro
    I recently installed in a strat pickups with unmagnetized alnico (I forgot to do this). Magnets new, in pickups have not been established. The guitar sound was is quiet (at all three singles). I could not understand why. Then I remembered that magnetized - not done.
    However, the signal from the guitar was.
     
  11. Zepfan

    Zepfan Poster Extraordinaire

    Posts:
    8,962
    Joined:
    Nov 30, 2013
    Location:
    Horn Lake, MS
    Pickups are electro magnets. Once current is introduced there will be some electro magnetism to make the pickup work, just not much.
    I thought all the "Goldfoil" magnets were made of rubber like some of the refrigerator magnets you get.
     
  12. dsutton24

    dsutton24 Doctor of Teleocity Ad Free Member

    Posts:
    10,199
    Joined:
    Dec 29, 2010
    Location:
    Illinois
    Now, how could that possibly be? There's no source of current in a guitar to create an electromagnet. If the magnets truly had no magnetic charge, there would have to be an outside source of magnetism of some kind in order for the pickup to produce any sound at all. Another pickup mounted on the same guitar might have enough influence to produce weak sound.

    Passive pickups are not electromagnets.
     
  13. Tony Done

    Tony Done Friend of Leo's

    Age:
    74
    Posts:
    4,970
    Joined:
    Dec 3, 2014
    Location:
    Toowoomba, Australia
    ^^^A working pickup is an electric generator. In the absence of a magnet, would the earth's magnetic field, or the residual magnetism in the strings be enough to make it work? I might try the experimental approach on that. :)
     
  14. Deneb

    Deneb Tele-Afflicted Ad Free Member

    Posts:
    1,607
    Joined:
    Feb 16, 2011
    Location:
    Ukraine, Dnipro
    I think in my case, the non-magnetized magnets have minimal charge. Laws of physics - has not been canceled. :) If anyone is interested, I can measure the strength of the magnetic field unmagnetized alnico rod.
     
  15. Zepfan

    Zepfan Poster Extraordinaire

    Posts:
    8,962
    Joined:
    Nov 30, 2013
    Location:
    Horn Lake, MS
    There's a very very small amount of electrical current that flows to your guitar's electronics from the amp when you plug it in that energizes the pickups. Talking about milli-volts. Plug a cord into your amp and turn it on, check the exposed end with a voltmeter set to 200m on the DC side and you'll get about .2 to .5 milli-volts.
     
  16. dsutton24

    dsutton24 Doctor of Teleocity Ad Free Member

    Posts:
    10,199
    Joined:
    Dec 29, 2010
    Location:
    Illinois
    You're seeing either leakage or noise being induced into your meter. .2 mv across 6000 ohms (give or take) yields .00000003 amps, that's insignificant.
     
  17. Zepfan

    Zepfan Poster Extraordinaire

    Posts:
    8,962
    Joined:
    Nov 30, 2013
    Location:
    Horn Lake, MS
    Your guitars electronics need the small energizing current to make them work since they are passive. All electro-magnets or electric generators need to be energized to work.
     
  18. JustMike

    JustMike TDPRI Member

    Age:
    60
    Posts:
    6
    Joined:
    Apr 11, 2016
    Location:
    SoCal
    There's a very common misconception of what a pickup is. It is a generator. A magnetic field moving across a wire induces a voltage in the wire, or many thousands of wires segments in a pickup coil. The purpose of the magnet is to magnetize the guitar string. Then this magntized section of string moves over the coil producing the voltage across the coil. The magnet is stationary in respect to the coil, so the magnet doesn't induce voltage in the coil. Once the strings are magnetized, you could remove the magnet and the pickup would still work, if the strings were to lose their magnetization they would induce less voltage in the pickup coil.
     
    teleaddicted likes this.
  19. Zepfan

    Zepfan Poster Extraordinaire

    Posts:
    8,962
    Joined:
    Nov 30, 2013
    Location:
    Horn Lake, MS
  20. JustMike

    JustMike TDPRI Member

    Age:
    60
    Posts:
    6
    Joined:
    Apr 11, 2016
    Location:
    SoCal
    Pickups will only produce on the order of 100 millivolts... give or take. This is why they need an amplifier. The pickup coils have a DC resistance of 6-15K ohms, a speaker has a DC resistance of 4-16 ohms. The difference in these impedances will require a proportional increase in current if trying to drive a speaker with a pickup. This is why you use an amplifier between pickups and speakers. Passive just means there is no amplification going on. Active pickups include an amplifier which is why you put a battery in the guitar (to power the amplifier)
     
IMPORTANT: Treat everyone here with respect, no matter how difficult!
No sex, drug, political, religion or hate discussion permitted here.


  1. This site uses cookies to help personalise content, tailor your experience and to keep you logged in if you register.
    By continuing to use this site, you are consenting to our use of cookies.