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Re: Weak pickup magnets


 
9/2/1997 8:00 PM
Mark Hammer
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Re: Weak pickup magnets
Can't remember where I read it, but I seem to recall that P-90's use *two* magnets, with the two side-to-side-polarized magnets attached to the base of the centre slug with the adjustable screws/polepieces, like so:  
 
N<-------->S slug S<-------->N  
 
This results in the centre-slug being one polarity, and the magnetic field extending from the polepieces to the opposite poles at the sides of the pickup. It's the magnets sticking out from the sides of the coil that yields the hotter output (the Fender Lace Sensor is an example of this principle taken even further, with magnetically conductive material extending up the sides of the coil so that the field goes from the centre of the coil to the adjacent area on the top of the pickup).  
 
Now, bear in mind that two magnets arranged as above will not "want" to stay together unless forced to do so by glue or some other means. Should that means of keeping them pointed in the manner illustrated fail in any way (e.g., glue dries out and one or both magnets break off), the natural inclination of the magnets is to stick to the centre slug like so:  
 
N<------>S slug N<------->S  
 
This makes the polepieces essentially neutral, in a magnetic sense. The output will drop noticeably, although there will still be output. The fix is to simply re-orient the magnets as illustrated in the first arrangement.  
 
Now I remember where I read it, it was in Vintage Guitar magazine, and was either George Gruhn's or Seymour Duncan's column.  
 
Now, having said this, I had something that looked like a P-90 on an old Epiphone Coronet, and it had only ONE bar magnet, and kind of a wimpy output. Was it a different kind of P-90? I dunno. The magnet WAS kind of weak however. The dual magnet arrangement should be able to provide a very decent output level, even with magnets that seem to barely tug much.  
 
I say corroborate (or refute) my advice before proceeding any further. The fix may be as simple as turning a magnet around.  
 
Good luck
 
9/3/1997 6:55 PM
David Axt
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Mark,  
 
You is da Man! Thanks for your response. I will try it. A friend told me stroke a stronger bar magnet on the weak magnet in one direction. This will remagnetize the weak magnet some how.  
 
I'll try this along with your "fix" and let you know. Thanks.
 
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