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Demagnetized Pick Up after Guitar Repair?

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  • Demagnetized Pick Up after Guitar Repair?

    hello everyone!
    strange situation after picking up my guitar from the repair shop (set up + fret levelling).
    First it's a Fender Jazzmaster Custom Shop (Japan) The Ventures limited edition and I believe it carries Seymour Duncans JM1 (B and N)
    The tech tells me over the phone that the neck pickup is demagnetized to which I ask what are my options and get as a reply that there's a tech who could re-work the magnets
    So, I think... maybe it was like that forever and I did not notice before, or just like it the way it is.
    I pick up the guitar and bring it home and there is something going on with the neck pick up. It sounds quieter than the bridge's and it's kind of uneven with less gain on the 3rd and 4th strings.
    I poked the poles with a small allen key and get a sound from all 6, however when i do the same on the neck pickup i notice that the magnets attraction force is bigger.
    As I have recorded something with that same guitar earlier this week I decided to compare wave files (fortunately I recorded rhythm guitars straight to the board using the Neck pickup on the left channel and the Bridge on the right one).
    I set up the levels so that the neck pickup matches the level from the old recording and when i try the bridge pickup i se it's noticeably quieter. about 10 dB RMS (an 3 dB quieter peaks)
    I'm a little bit confused as the guy says he double checked the wiring.
    Summarizing:

    - sudden drop in gain on 1 pickup in the course of 3 days (-10 dB RMS, -3 dB peaks). maybe the pick up was much closer to the strings before? (in any case the difference now with the bridge pickup is of about 9 dB RMS)
    - magnet attraction force noticeably different and smaller on neck pickup (maybe they are supposed to be like that by design? the strings vibrate less closer to the bridge and the PU needs to seat higher and maybe the magnets to be stronger as well?)
    - the PU selector works good, no strange noises when switching PUs (I deoxited it myself a few days ago along with the tone and volume pots)

    i'm thinking about strange magnetic fields the guitar could have been exposed too and my car is hybrid, the battery is in the back and the guitar was in the trunk... but it's not the first time.

    any ideas?

    thanks!

  • #2
    Please attach your direct recorded guitar files so we hear what are you talking about.
    Juan Manuel Fahey

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    • #3
      Some shops use fine steelwool to polish frets. Works great but leaves a mess of steelwool debris. So some think it's a good idea to collect the pieces with a (neo) magnet. Guess what happens if the magnet ever gets within maybe 1cm distance to the neck PU?

      Remember that (de)magnetization is an immediate effect and even quickly wiping with the magnet across/above the PU magnets suffices.
      Last edited by Helmholtz; 10-23-2020, 02:35 PM.
      - Own Opinions Only -

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      • #4
        hola senyor Juan Manuel!
        here the wave files for the NECK and BRIDGE pickups BEFORE and AFTER
        Guitar is going to the board through a tube preamp which I like to saturate a little bit, so whatever clipping you hear in the files this is (for me) "normal"
        BRIDGE pickup was BEFORE a little brighter and had slightly more gain (i did not match the PREAMP GAIN perfectly) and this could be because of GAIN settings on the preamp, pickup height after the setup work or the new strings (had fender 009s before and washburn 009s now)

        vielen dank Hr Helmholtz for your addition,
        quick reply, the frets needed to be filed (reduced in height) and not just polished (they were pretty clean)... but maybe they did it anyway?

        i'll let you hear the files and we can continue the conversation

        thx guys,
        Attached Files

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        • #5
          quick reply, the frets needed to be filed (reduced in height) and not just polished (they were pretty clean)... but maybe they did it anyway?
          Levelling leaves the frets rough and edgy. Always needs to be followed by re-shaping and polishing
          Last edited by Helmholtz; 10-23-2020, 04:08 PM.
          - Own Opinions Only -

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          • #6
            Originally posted by Helmholtz View Post
            Levelling leaves the frets rough and edgy. Always needs to be followed by re-shaping and polishing
            verstanden... and logic

            to add to the sound files shared


            Click image for larger version

Name:	NECK PU.jpg
Views:	154
Size:	404.4 KB
ID:	916425

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            • #7
              Ask the shop if they use steelwool and neos in the shop. If yes they should offer you to remagnetize the PU for free.
              - Own Opinions Only -

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              • #8
                i did after you email

                Looking for alternatives there's a guy who re-magnetizes pickups for $80 and a new one (I am waiting for Seymour Duncan to reconfirm it is the exact same) goes for $69

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                • #9
                  PU (re)magnetizing should not take more than 5 minutes.

                  Look here: https://music-electronics-forum.com/...974#post766974
                  - Own Opinions Only -

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                  • #10
                    ahhh... you're a connoisseur!
                    putting the magnets in line and approaching the pickup poles in a perpendicular fashion should not be a challenge
                    getting the right magnets and being able to measure the magnetic field maybe out of reach for me at the moment :/

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                    • #11
                      getting the right magnets and being able to measure the magnetic field maybe out of reach for me at the moment
                      The neos I got from Amazon. Not necessary to the measure magnetic field. My method fully charges the PU magnets just as Leo did.
                      - Own Opinions Only -

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                      • #12
                        i could give it a try. I mean, that pickup is destined to go into the trash can otherwise
                        care to share the AMAZON link?
                        I’ll re-read your post and try to digure out what the procedure is as i want to be sure i respect polarity, time, etc
                        it breaks my bxxxx to take the guitar apart now that it’s been properly setup

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                        • #13

                          care to share the AMAZON link?
                          Sorry, bought them at least 10 years ago. Should be easy to find.

                          want to be sure i respect polarity, time,etc
                          As said, the effect is instantaneous. So time doesn't matter.

                          it breaks my bxxxx to take the guitar apart now that it’s been properly setup
                          If - what I assume - your PU magnets have been demagnetized from the top, it should suffice to remagnetize the top poles only.
                          If you're careful this can be done without removing the PUs from the guitar.
                          - Own Opinions Only -

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                          • #14
                            thank you, I'm looking at AMAZON but they are a mess... nice place to find fridge magnets though
                            i am assuming the magnets diameter must match (approx.) the pole's diameter, with is 5 mm in my case
                            i am seeing 25 magnets piled up in your photo and think this adds to the magnetic force used to act on the pole
                            I found something that is 4.8 x 3.2 mm and has a holding force of 0.8 Kg from (what seems to be) a respectable US business (buymagnets.com)with a total cost (25x shipping incl) of $15. Any scientific way of determining how many magnets are necessary?
                            Then the next question would be how to be sure I am polarizing the Pickup in the right way (north or south). I've read the NECK and BRIDGE have inverted polarities with respect to each other so they cancel noise when used together. I've read on the SEYMOUR DUNCAN specs (vintage jazzmaster neck) that this one has a reverse polarity winding (RWRP)
                            Last edited by TelRay; 10-24-2020, 03:20 AM.

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                            • #15
                              To anyone who is recharging the magnets ,Most JM pickups are rw/rp so you need to charge them accordingly
                              "UP here in the Canada we shoot things we don't understand"

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