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Author
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Topic: To Change Polarity of Magnet on Pickup
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Jackiso
Member From: Yokohama, Japan
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posted 19 March 2004 05:56 PM
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Would need your expert advice on the folowing:
I have a Magnatone T8 table steel with twin pickups on each neck like a Stringmaster. During the process of dealing with its hum problem I found that on the front and mid neck the polarity of magnet of each pair of the pickup is made the same, i.e. Front:North/North, Mid: North/North, Back: North/South.
To make these pickups work like a humbucker, I would have to reverse the polarity of the magnet from North to South on one of the pickups on the front and mid neck. These Magnatone pickups are covered by metal plates which are riveted. Now my question is:
1.Could the magnet polarity be changed easily if I could ply open the pickup casing?
2. Would it be a safe job, not hurting the coil?
As the Magnatone is rather quiet under the hum free environment, I would not venture into tweaking the pickups if it involves a great risk of damaging the coils.
Appreciate very much your inputs.
Jack Isomura
Yokohama, Japan |
Rick Aiello
Member From: Berryville, VA USA
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posted 19 March 2004 06:35 PM
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Your pickups don't need to be "disassemled" to have the polarities of the magnets reversed.Simply placing the entire unit in the gap of a strong enough electromagnet ... and zapping it will do the trick. For example: Let (N) and (S) be the poles of the electromagnet ... and (n) and (s) be the poles from your pickup. Before "zapping" : (N)...(n)--(s) ...(S) After "zapping" : (N)...(s)--(n) ...(S) I could do it for you ... but shipping from Japan  Alnico magnets require magnetizing fields of about 3000 Oersteds ... A capacitor discharge electromagnet like these will do the job ... A well made DC electromagnet like this one will also work on Alnico 5. You should be able to find someone in your area that has one type or the other ... Large Neodymium magnets can also be used to charge/repolarize alnico ... but the problem with them is that once they "latch on" ... its very difficult to pull them off ... You end up sliding them to get them apart and that can degauss them and/or change their orientation. Thats why electromagnets are preferred ... Hope that helps ... ------------------
www.horseshoemagnets.com [This message was edited by Rick Aiello on 19 March 2004 at 07:02 PM.] |
Donny Hinson
Member From: Balto., Md. U.S.A.
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posted 19 March 2004 07:19 PM
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Unless the magnets are easily removed (doubtful, at best) so you can just turn them over, this isn't a job for an amateur. Also, be advised that demagnetizing/magnetizing magnets while they are still in the pickup could damage the coil (due to the high induced voltage and current). Personally, I'd try shielding all the wiring first (to eliminate any hum you have), and then (if you prefer the "humbucking tone"), I'd farm out the pickups to someone with the experience and equipment to do the job right. That's my2cents worth!  |
Jackiso
Member From: Yokohama, Japan
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posted 19 March 2004 11:16 PM
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Rick,
Wow! zapping can change the polarities!! I've never thought that's possible. But it looks like a pro's job with equipment. Too scarely for an amatuer like me. I would try to find an expert locally. Thank you.Donny,
I have so far tried almost every means to eliminate hum leaving a humbucker option as the last resort. If the hum problem narrows the Magnatone's playground extremely, I would turn to pros either for reassembling the pickups or for zapping. Thanks guys for great advice,
Jack |
William Peters
Member From: Effort, Pennsylvania, USA
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posted 20 March 2004 08:30 AM
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Jack,There is more to making a humbucker than just reversing the magnets. One of the coils has to be wound backwards to the other. Otherwise the two coils will cancel the signal from the strings, instead of the induced hum from external sources. Bill |
Rick Aiello
Member From: Berryville, VA USA
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posted 20 March 2004 10:37 AM
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Damaging a pickup during a re-mag or polarity shift usually is associated with the physical "movement" of the pole pieces/blade when the magnetizing field is applied ... shorting the coil.3 kOe is fairly weak in terms of Magnetizing Force (H) ... so I wouldn't be concerned with any induced current causing damage ... but it sure is enough to "yank" the components around. Alot of pickups have to be re-maged as a whole unit ... since the pole pieces are in direct contact with the coil ... Trying to remove the pole piece will definitely short the coil. The most difficult pickup re-mag that I have done so far was an unusual old National ... It had 4 bar magnets ... two laying parallel to the coil on each side ... encased in a ferrous enclosure. The orientation of the bars was (S) facing up with a (N) conduit running underneath and up to the pole pieces. Basically the top of the pickup had the outer fringes (S) while the pole pieces were (N). Jason told me that I'd short the coil if I tried to pry open the case ... so I had to come up with a plan to do the re-mag all 4 bars at once ... and having it "bi-polar" on each side made the standard set-up for re-magin' impossible. I was "sweatin' bullets" when I applied the juice ... but it all went well and I got them all up to around 800 gauss (they were at 350 prior). ------------------
www.horseshoemagnets.com |
Paul Osbty
Member From: Seattle, Washington, USA
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posted 20 March 2004 02:01 PM
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Is rotating the mounting the 2nd pickup (of the North/North combinations) by 180 degrees not possible? |
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