Supro Lapsteel PU magnets question

Karl Oberlander · Post by **Karl Oberlander** » 13 Feb 2004 3:21 pm

I recently acquired a mid '60's Supro Lapsteel and when I took the pickup cover off to check out the wiring etc. I noticed that the block magnet on the far side had been replaced with a piece of wood cut to the same shape as the magnet on the other side. These magnets are the ones that the pickup cover sits on and the screws go down through them into the base plate.

I left the magnet(s) and cover plate off so I could take the magnet to a shop and have one cut to match. When I strung the thing back up I noticed that the three high side strings had plenty of volume but the three bass side strings had very little volume even after I adjusted the poles up a bit.

This pickup is the one that has the offset pole pieces the three for the bass side are towards the nut and the three for the treble side are towards the bridge. The one magnet that was on the pickup was on the bass side.

Anyone know what exactly those magnets are for? And why removing one on the treble side makes no difference but removing one on the bass side changes the output?

Thanks in advance for any tips.

Kobe

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Gibson D-8 Console Grande - Stringmaster T-8 - Alkire EHarp D-10
Fender Super Reverb
kobe@austin.rr.com
http://home.austin.rr.com/kobeco

Rick Aiello · Post by **Rick Aiello** » 13 Feb 2004 5:09 pm

Bill Creller has the answer to your question here ...
http://steelguitarforum.com/Forum2/HTML/004717.html

As for why the pickup still functioned without the one magnet ... the steel pole pieces retain magnetism even when the magnetizing source is removed. What you were experiencing was "induced residual magnetism."

By the way, putting a second magnet in place of the aluminum block (in your case the wood) ... Correctly oriented ... both (N) poles up and both (S) poles down (or visa versa} ....

Would give you the basic setup of a Fender Boxcar/Trapazoid ... minus the string thru the coil bobbin of course.

I've make these ... they are "Rippin" ..

Hope this helps ...

PS The reason why the bass strings didn't "sound out" like the treble strings with the alnico block removed ... the bass frequencies need more "juice" ...

Ever seen a Fender Dual Professional/Custom with the trapazoid pickups ... that magnet is 2X the size of the treble.

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www.horseshoemagnets.com 
[This message was edited by Rick Aiello on 13 February 2004 at 05:35 PM.]

Donny Hinson · Post by **Donny Hinson** » 13 Feb 2004 5:48 pm

You have to have some magnetism for the pickup to generate the signal voltage. (A conductor moving through a magnetic field is what generates the voltage.) No magnetic field...no signal. The one magnet that was missing was probably cracked, and was causing a buzzing sound. The owner was smart enough to realize that it would still work (albeit not as well) with one magnet.

Fortunately, there's dozens of sources for magnets on the web!

Karl Oberlander · Post by **Karl Oberlander** » 14 Feb 2004 5:36 am

Thanks guys,

Rick, are there two magnets or kust one and an aluminum block fo the other one? I'm confused. It would be really easy to cut a piece of aluminum on that block shape.

Kobe

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Gibson D-8 Console Grande - Stringmaster T-8 - Alkire EHarp D-10
Fender Super Reverb
kobe@austin.rr.com
http://home.austin.rr.com/kobeco

Rick Aiello · Post by **Rick Aiello** » 14 Feb 2004 6:19 am

There was just one ... at least on all the ones I have done (re-maged).

As Bill C. said in the other post ... it forms kinda a "pseudo" horseshoe . The alnico block is the flux source and the straps act as magnetic conduits.

Simple in form ... very effective.

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www.horseshoemagnets.com

Rick Aiello · Post by **Rick Aiello** » 14 Feb 2004 7:33 am

While I'm thinkin' 'bout it ...

The "one magnet" approach was probably a way to get around the utility patent held by Fender (for the 2 magnet block system).

Seems there were lots of lawsuits back then ... which led to very clever ways to side-step existing designs.

If it was my steel ... I'd employ my usual "Tim the Toolman" approach (more power)

... I'd get an alnico block and fashion a treble side magnet.

You probably can't find that exact size so you could stack smaller ones together or use mild steel in conjunction with the alnico to match the size.

Having a custom alnico block made would be more expensive than the entire guitar

The only thing to be concerened with is the orientation of the field. "Bar" magnets are oriented along their length ... "Block" magnets are oriented through their thickness ...

You want block ... hope this helps

Karl Oberlander · Post by **Karl Oberlander** » 14 Feb 2004 8:29 am

TRhanks Rick,

That clarifies this very well. I'll have an alum. block cut for it at the local machine shop. I'll ask them if they can do the magnet as well.

Where would one find the ALNICO V material?

Thanks,

Kobe

------------------
Gibson D-8 Console Grande - Stringmaster T-8 - Alkire EHarp D-10
Fender Super Reverb
kobe@austin.rr.com
http://home.austin.rr.com/kobeco

Rick Aiello · Post by **Rick Aiello** » 14 Feb 2004 8:40 am

This is a one of my favorite sites:

Magnet Sales

These folks carry lots ... but I believe they have a $50 minimum ??

All Magnets / Magnet Source

Ferrite magnets (ceramic) are good alternatives ... cheaper and more available sizes.

Alnicos are very difficult to "machine" ... brittle ... so getting the correct size/orientation is the issue.

If need be ... I can change the orientation .. so if you find the appropriate "bar", I can re-orient it for you.[This message was edited by Rick Aiello on 14 February 2004 at 09:13 AM.]

Jason Lollar · Post by **Jason Lollar** » 15 Feb 2004 2:41 pm

I have never seen one of those that was stock that only had one magnet. they work as rick described.
You can get signal without a magnet from capacitance of the coil and if you have the pickup near an electromagnetc field like a transformer in your amp or anything carrying electricity of course a transformer or motor would make the pickup louder than just holding it near an electrical source.

Rick Aiello · Post by **Rick Aiello** » 23 Feb 2004 2:10 pm

Just got a National in for a re-mag ... that same style.

This one had 2 identical magnets ...

That's (4) one magnet jobs to a (1) two magnet job ... so far ...

I think I'll keep a runnin' count.

Karl Oberlander · Post by **Karl Oberlander** » 23 Feb 2004 2:51 pm

Rick,

I had a machine shop cut me an aluminum block for this one and it now sounds loud and proud. I'm amazed it works so well but it literally screams. I don't think I'll try to get a matching alnico for this. That is unless you are going to make up a bunch of them, then I'd buy one to try out.

Thanks again,

Kobe

------------------
Gibson D-8 Console Grande - Stringmaster T-8 - Alkire EHarp D-10
Fender Super Reverb
kobe@austin.rr.com
http://home.austin.rr.com/kobeco

Rick Aiello · Post by **Rick Aiello** » 23 Feb 2004 4:10 pm

Kobe ... you must have ESP.

First thing I did when I saw the pickup was make technical drawings of the magnets.

They will be added to my new ... L-Series replacements.

You think those are "powerful" ...

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www.horseshoemagnets.com

emil noothout · Post by **emil noothout** » 27 Feb 2004 3:59 am

a friend of mine had a similar problem with a National New Yorker: the top strings sounded ok, but the three bottom ones were virtually dead. She had it repaired, and they told her the pick-up had six coils, and three had gone bad and had to be rewound. Anyone ever heard of a pick-up like that? (it sounded pretty strange to me)

Rick Aiello · Post by **Rick Aiello** » 27 Feb 2004 9:15 am

Jason Lollar has made some multi-coil custom jobs ...

Alan Kirk · Post by **Alan Kirk** » 7 Nov 2004 9:27 am

Okay, so let's say, theoretically, some dummy (who shall remain nameless) got mixed up and didn't know which piece of metal went on which side of the pickup, how would he tell? (Aluminum not magnetic?).

And if he did figure out which piece of metal went on which side of the pickup, how does he tell which side is N and which side is S?

Thanks.

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Bill Creller · Post by **Bill Creller** » 14 Nov 2004 1:21 pm

I have had a few Supro pickups apart, and they all had a magnet at one end and a matching (size-wise)Piece of aluminum stock on the opposite end. Maybe that made it sort of a horse shoe.
Bill

Rick Aiello · Post by **Rick Aiello** » 16 Nov 2004 3:40 pm

Add to the list ...

1 alnico magnet block and 1 rust-free ferromagnetic slug (my guess ... 400 series stainless steel).

This particular magnet was a mess too .. as deqaussed and "random" (as in orientation) as I've ever seen one ..

It ain't now

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Aiello's House of Gauss


My wife and I don't think alike. She donates money to the homeless and I donate money to the topless! ... R. Dangerfield