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Thread: Properly charging magnets with MojoTone magnetizer.

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    Properly charging magnets with MojoTone magnetizer.

    I am new to pickup making. I purchased the Mojotone magnetizer, which is basically a vise with two powerful magnets on each jaw. One South and one North.
    Can someone tell me the proper way to use this magnetizer.
    The magnets I have are supposed to be already charged but I want to make sure they are fully charged.
    I put a magnet through it and noticed I messed up the magnet.

    Could someone write down the steps to take for properly charging a magnet.
    If the compass needle is attracted to the magnet then this means the magnet is South. Right?

    I would like to know what side of the magnet goes into the charger. Also does the magnet go in vertically or horizontally? Do you close the jaws on the magnet and leave it there for some time or do you just pass it through the jaws once or a few times.
    I believe the orientation of the magnet must be determined prior to placing the magnet through the charger. I think this was my problem and I may have reversed the magnet polarity. If this happens, what is the remedy to restore the magnet?
    Simple steps to take would be really appreciate and it would clarify everything for me.
    MojoTone does not provide any instructions with this tool.

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    Roberto Venn uses those so I am familiar with that. One jaw is south and the other is north- determine which is which with a compass- opposites attract so the north end of the needle will point to south. Dont waive the pickup magnets or pass them through with any sort of motion- Put the magnet or assembly between the two jaws of the vice so south touches the south jaw and north touches the north jaw (as I recall- check it)- hand tighten the jaws together- doesnt take any real pressure then unscrew the jaws quite a ways and pull the magnet or assembly out but dont move it sideways- pull it in the shortest direction you can that takes the most pressure. Magnetising is instantaneous
    If you get the polarity reversed just put it in the other way and do it again

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    Thanks very much for the thorough reply Jason. I was not aware that you are a contributor here. I am very new to this forum.
    Actually, after messing up the magnet the first time. I looks like I did exactly as you suggest, just by chance and managed to restore the magnet.
    I placed the magnet in the center of the two jaws and closed both jaws lightly on the magnet. I kept it there for a few minutes. Then I pushed the magnet out lengthwise with the provided piece of wood shim, which came with the magnetizer. I am not sure if this is what you mean in your explanation. I don't know what you mean by not moving it sideways. You mean the side of the magnet? The narrow sides, as opposed to the larger surface flat sides?
    My magnet was always touching the magnetizer magnets on the large surfaces (top and bottom), NOT the sides of the magnet.
    My magnet was oriented the same way as the jaw magnets are? Is this correct?

    When I took the magnet out of the magnetizer, instead of pulling the magnet upwards out of the magnetizer, I pushed it out lengthwise, with the aid of the piece of wood, which came with the unit as a shim between the two jaws.

    I hope this is what you are suggesting.
    After removing my magnet, I checked the magnet strength on a large cast iron surface and it had quite a strong pull to it, much more than when I lower its strength before. The pickup works well, so I must have done something right. I hope I did exactly what you suggest.
    I do wish MojoTone or someone would do a short YouTube video demonstrating the technique, so its visual.

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    I think Jason is suggesting that you pull the magnets straight up out from the wide opened jaws. Sliding the magnet out the end essentially skews the flux lines diagonally towards the end of the magnet that was last in contact with with the mags. You may get some inconsistencies in the Gauss along the edge of the magnet doing it this way.
    Humbucker magnets are always magnetized across the 1/2" width dimension, never from top to bottom through the thin 1/8" dimension as it sounds like you may have done. Alnico is generally pre-oriented as it cools from the foundry if you try to magnetize it in a different orientation it won't hold the charge very well. It will never hold a charge across the thinest dimension the way Ceramic and rare earth magnets can.

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    Alnico is generally pre-oriented as it cools from the foundry.
    Only true for anisotropic magnets like A5 and higher.

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    David King - Thanks fore confirming this for me. This is how I started doing it. I place the magnet between the closed jaws, then open the jaws and pull the magnet upwards, out of the vise straight up. Not sideways across the jaws.
    Yes, prior to this I pulled the magnet out sideways and that is what messed up the magnet. The magnet had very little magnetic pull. I must have done it right recently because the pup I wound is very good. 16+K for a humbucker and when I cut the coils, I get about 8K and it balances well with the two Strat pups.

    Just to be absolutely certain of what you and Jason are saying.
    I put the magnet in between the jaws so that one 1/2" surface is sitting flat on the N jaw and the other side 1/2 surface is sitting flush against the S jaw. This way the magnet wants to stay in the center of the jaw magnets. Then I close the jaws on the magnet, the jaws being 1/8" apart when closed, with the magnet snug in between the jaws.
    Is this what you are suggesting? If this is NOT what you are saying I want to know. However, it still worked for me and the magnet was magnetized with a strong pull but it would be great to definitely know. Its hard to convey something in text, where a picture is worth a thousand words.

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    Having read your reply again. I think I still did it the wrong way. If I understand you correctly, I charged the magnet top to bottom, NOT side to side.
    I think you are suggesting to put the magnet in the vise so that the 1/8 edges are facing and touching the jaw magnets.
    Side to side, so that one 1/8 side of the magnet touches the S jaw and the opposite 1/8 side touches the N jaw. This may be what you are saying.
    Please confirm.

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    yes 1/8 X 2.25 or 2/15 face will be north and the other south.
    typically the longer the distance between poles on alnico the stronger the magnet so a magnet with 1/8 between poles is super weak- a magnet with 1 inch between poles is much stronger unlike ceramic that is generally charged through the thickness

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    Quote Originally Posted by Lollar Jason View Post
    yes 1/8 X 2.25 or 2/15 face will be north and the other south.
    typically the longer the distance between poles on alnico the stronger the magnet so a magnet with 1/8 between poles is super weak- a magnet with 1 inch between poles is much stronger unlike ceramic that is generally charged through the thickness
    just purchased this item from aliexpress, seems to work with a voltmeter.
    should be helpfull to select magnets.
    https://www.aliexpress.com/item/Tesl...618c4c4dOtex9p

    basscu

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    Looks interesting, but the ad you linked to does not provide any details on scale or up to what maximum Gauss/Tesla level it can read, which of course must be stated in the spec sheet or user manual accompanying it.
    Can you please post that data when you get it?

    Plus maybe some actual use description when you measure something.

    Thanks.

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    Juan Manuel Fahey

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    Quote Originally Posted by basscu View Post
    just purchased this item from aliexpress, seems to work with a voltmeter.
    should be helpfull to select magnets.
    https://www.aliexpress.com/item/Tesl...618c4c4dOtex9p

    basscu
    Interesting.
    Do you know maximum field intensity it can measure?
    And what is the conversion factor (mV per Gauss?), its not stated inn the Aliexpress link.

    I fear its not enough for pickup duty; it will definitely not work for me, who make speakers.

    I just checked a typical Hall sensor (now called Holzer for some obscure reason) and found it unsuitable for my use, not sure it is enough for pickups, what do you say?:
    https://www.sunrom.com/p/ss49e-hall-...-linear-analog

    Direct sensor output is:


    full scale is +/-100mT or +/- 1000Gauss ... is that enough?

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    Juan Manuel Fahey

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    HB bar alnico magnets are typically below 1000G (A5: 700..800G) at the center of the pole faces, increasing towards the edges. Ceramics mostly above 1000G. A5 strat poles can go up to 1200G. Comparisons are still possible, if you use a shim (e.g. 0.1 inch thickness) between pole and sensor.
    Don't rely on sources which speak of values in the 20...30G range like in this article:
    https://musicalilluminism.wordpress....l-pickup-tech/

    Such low Gauss values are obtained using something like the R.B. Annis Model 25 magnetometer (http://www.rbannis.com/products/magnets.html). These analog magnetometers measure an average B value at an undefined distance (maybe an inch or so) from the pole, which is not comparable to the real pole strength. The axial field strength decreases with the distance (d) between the pole and the sensor approximately according to 1/d for short distances and evolves into a 1/d dependance at large distance.

    (I am sure "Holzer" is some misspelling of Hall, maybe produced by a voice translating maschine.)

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    Last edited by Helmholtz; 10-25-2018 at 04:04 PM.
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    chinese gaussmeter?

    Quote Originally Posted by J M Fahey View Post
    Looks interesting, but the ad you linked to does not provide any details on scale or up to what maximum Gauss/Tesla level it can read, which of course must be stated in the spec sheet or user manual accompanying it.
    Can you please post that data when you get it?

    Plus maybe some actual use description when you measure something.

    Thanks.

    there's no manual nor any specsheet or details, [there are many shops on ali selling things they don't even know what they sell.)
    anyway, my idea was that it could be something similar to what has been seen here as DIY projects.
    I "measured" the alnico5 mags inside a jazzbass-bobbin, reading 2,93, ceramic mag appr. 24 x10 x6mm, magnetized through 10mm, reading 3,12,
    and a neo-mag 15x 15 x 5mm, through 5mm, measuring 4,1. all in the 20 volt range of the meter. I measured a strat-bobbin with a2 mags measuring from 2,16 to 2,25.
    I'll contact the shop for some info and let you know.
    greetings from duisburg / germany

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    Quote Originally Posted by Lollar Jason View Post
    Roberto Venn uses those so I am familiar with that. One jaw is south and the other is north- determine which is which with a compass- opposites attract so the north end of the needle will point to south. Dont waive the pickup magnets or pass them through with any sort of motion- Put the magnet or assembly between the two jaws of the vice so south touches the south jaw and north touches the north jaw (as I recall- check it)- hand tighten the jaws together- doesnt take any real pressure then unscrew the jaws quite a ways and pull the magnet or assembly out but dont move it sideways- pull it in the shortest direction you can that takes the most pressure. Magnetising is instantaneous
    If you get the polarity reversed just put it in the other way and do it again
    Thanks so much for sharing this. Great info.

    As for the Mojotone magnetizer polarity:

    The Mojotone magnetizers are labeled opposite of what they really are. If you want North top polarity, you put the pickup in so the tops of the pole pieces are against the North jaw. It's technically south polarity, but this way of labeling the magnets is far more intuitive and has made it much easier to not make mistakes when charging reverse polarity pups.

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