Magnitizing magnets??

[David Schwab]

The problem seems to be when I release the alnico bar from the vise one side of the alnico bar wants to stay stuck to one neo, (either the N or S ) and that causes problems.

I just pull the magnet through. I have it touching the neos on both sides. Of course I'm not trying to get less than a full charge, but you can use plastic or wood spacers between the neos and the alnico magnet.

One thing you may notice is that the North and South poles of a magnet never read the same. This is true of every alnico I have ever checked.

I can't say I notice any tonal difference with a 10 G difference in charge.

[ken]

I got Gingery's book here on how to build a magneto magnetizer & it calls for two 6lb spools of 18 gauge wire

Copperheadroads, I built Gingery's magnetizer a couple of years ago, but it didn't have quite the 'oomph' I thought it should. I built a cap discharge supply for it.

ken

[copperheadroads]

Copperheadroads, I built Gingery's magnetizer a couple of years ago, but it didn't have quite the 'oomph' I thought it should. I built a cap discharge supply for it.

ken

Thanks ,I really didn't consider if it had enough jam to fully charge magnets

[Stratz]

what I do us use wood or foam fixtures to raise the magnet up off the plate. The more it is raised, the less the charge is reduced.

Are the bar magnets pretty much evenly charged using this method Sonny?

Thanks to all for the replies. I'd like to hear more from others who use neos or electrio-magnetizers to charge bars.

Rob.

[J M Fahey]

I have two homebuilt electric magnetizers but my needs are different, I make speakers so I need to magnetize ceramic rings already mounted in their mkagnetic structures, which are already soldered to the speaker frames, this complicates things a lot.
The "small" one is at my shop, can magnetize up to 102 mm (4") diameter rings, what's used in Jensen "Q" , Celestion "L" , etc. speakers or smaller (Jensen "R", Celestion "D" size, etc.)
This one is my bread and butter machine and is used every week.
Runs on 220V and pulls 44 Amperes. Yes, that's around 10KW.
Since my shop is not registered as an Industry (which would bring tons of Taxes, regulations, inspections, all kinds of trouble) my "home" Electrical installation stands only around 15 A, so I have a thick 20 yard cord with (very well insulated) car battery type clamps and on holidays or at night I go to the Electrical Distribution box on the street and get power straight from it.
The other machine lives at a friend's Factory 30 miles away, because it uses fullwave rectified 3x380V at around 50 or 60 Amperes, impossible at home.
It magnetizes rings up to 150mm (Celestion Vintage 30 size).
Now i'm building a bigger one for 190/220 mm rings (think EVM15L/JBL biggies/Black Widows) but will make it Capacitive Discharge because the "brute force" gets out of hand.
Big problem is getting the tons of capacitors needed at a reasonable price.
Not forgetting I'm 6000 miles away from the USA.
Oh well.

[SonnyW]

Are the bar magnets pretty much evenly charged using this method Sonny?

Thanks to all for the replies. I'd like to hear more from others who use neos or electrio-magnetizers to charge bars.

Rob.

It depends on what you define as evenly charged. There is variation in the magnetizer and also variation when demagnetizing. I think it depends on the structure of the particular magnet, as much as anything else, There is always more charge at the ends. And remember when installed in a humbucker there will be less variation at the polepieces than along the bar edges.

You guys made me clean off my bench for this, not that it didn't need it. I did a little testing with the fixtures. I took an ordinary A5 magnet (from Dennis) and gave it a full charge with the M-24C. I measured the gauss levels at 6 points along each edge and recorded them. I calculated the total variation (range %) and average gauss. Then I used my different combinations of fixtures to degauss that magnet and recorded the same 12 measurements for various heights. In the first part of the test, I kept the fixture stationary in the center of the plate and gave it 3 bursts of 2 seconds each. I recorded all that data. Then I repeated some of the same tests, but instead of leaving the fixtures stationary in the center of the plate, I left the demagnetizer on for about 10 seconds and moved the fixture around on the plate, which is what you are supposed to do for best degaussing. My notes are in the attached photo. I'll summarize the results. On a fresh full charge I got 747 gauss with a 26% variation range. In stationary degaussing mode I got 2.1% reduction at 2 1/2 inches with 25% variation range, 5.9% at 1 5/8 inches with 25% variation range, 17% reduction at 7/8 inch with 28% variation range, 30.8% reduction at 1/2 inch with a 42% variation range, 78% reduction directly on the plate with a 97% variation range. Then in degaussing with motion directly on the plate I got 95.8% reduction with 89% variation range. Next I recharged the magnet as before and got 753 gauss with 28.7 % variation range. This is within 1% of the first charge. You can study the notes for the rest, but at 7/8 inches with motion I got a reduction of 28% and at 1/2 inches with motion I got 48%. There was a larger variation range with the motion than without, but a larger amount of gauss reduction. Here is a shot of my setup and a composite photo of my notes. Enjoy.

[Stratz]

Thanks Sonny, I really appreciate the amount of work you did and all of the data you posted.
I saved the pics of your drawings to review some more.

I cant build pickups with someone elses pre-charged magnets. I'll screw around with the neo's a bit more. If I cant get a better pattern I'll spring for the something like the M-24C and take it from there.

My father has a electro-magnetizer but I don't know which one, I'll have to call him and find out (I'm running low on vintage PE for repairs and he has a load of it so it's an excuse to call )
He had a pace maker installed Thanksgiving weekend 2 years ago so I imagine his wife is charging magnets for him.

Thanks again.
Rob.

[SonnyW]

Thanks Sonny, I really appreciate the amount of work you did and all of the data you posted.
I saved the pics of your drawings to review some more.

I cant build pickups with someone elses pre-charged magnets. I'll screw around with the neo's a bit more. If I cant get a better pattern I'll spring for the something like the M-24C and take it from there.

My father has a electro-magnetizer but I don't know which one, I'll have to call him and find out (I'm running low on vintage PE for repairs and he has a load of it so it's an excuse to call )
He had a pace maker installed Thanksgiving weekend 2 years ago so I imagine his wife is charging magnets for him.

Thanks again.
Rob.

I needed the data anyway so it wasn't that much trouble, and I had some slack time. I have had those fixtures for a while and used them but never got very scientific about it. One nice thing with this arrangement is if you don't like how it comes out it is easy to degauss it completely and start fresh. I have noticed though that the stronger measurements on the same magnets are often in the same spots, which makes me think it might have something to do with the magnet itself.

I am sure your dad would be smart to keep a distance from these with a pacemaker. If I accidentally leave scissors or any small metal tool near the M24C they will jump around when I turn it on. The effect is less with the demagnetizer, but if I don't hold down a fully charged magnet it will fly off.

[ken]

Supposedly Leo Fender used a magnetizer made from a truck starter to magnetize Tele magnets. Does anyone know how he did this?

ken

[copperheadroads]

Supposedly Leo Fender used a magnetizer made from a truck starter to magnetize Tele magnets. Does anyone know how he did this?

ken

I'd love to know how to do that
& the magnetizers they used with two large coils and how they hooked it up to an old 6 volt car battery. as they used the battery “it would become weak and hardly magnetize the magnet slugs and would have to be charged again overnight.

[SonnyW]

I'd love to know how to do that
& the magnetizers they used with two large coils and how they hooked it up to an old 6 volt car battery. as they used the battery “it would become weak and hardly magnetize the magnet slugs and would have to be charged again overnight.

I know that's the story from Seymour about the car batteries getting weak, but there was another magnetizer that was a lot more powerful if you believe the old timers on the steel guitar forum. Some of them actually worked at Fender. I remember one post where someone said that if you got within a hundred feet of that thing it would stop your watch, and another old timer jumped in and said yes it toasted two of his watches while he was there.

Edit: I found that thread, here it is.
http://bb.steelguitarforum.com/viewt...ff60cc92205dba

[Joe Gwinn]

Now i'm building a bigger one for 190/220 mm rings (think EVM15L/JBL biggies/Black Widows) but will make it Capacitive Discharge because the "brute force" gets out of hand.
Big problem is getting the tons of capacitors needed at a reasonable price.

You might find US Patent 4,258,405 "Electrical Impulse Generator" to Steingroever pertinent. While Steingroever used mercury-pool Ignitrons (Ignitron - Wikipedia), one can as well use those big hocky-puck SCRs for a magnet charger. Steingroever is making metalworking tools.

You will want to use laminated iron polepieces, so the impulse energy isn't spent heating the iron with eddy currents.

If you are not yourself an electrical engineer, I would find one to help you. This circuit is quite capable of destroying itself, and of throwing a burnt body across the room.

[J M Fahey]

Thanks a lot.
Interesting patent. The basic charging mechanism is the classic one, but he saves energy and overheats less the coil, good in a high production (China?) machine.
I'm happy with magnetizing up to 20 or 25 speakers a day.

[Joe Gwinn]

Thanks a lot.
Interesting patent. The basic charging mechanism is the classic one, but he saves energy and overheats less the coil, good in a high production (China?) machine.

It also saves the capacitors from degradation from reverse currents while the tank resonates. This is a big advantage of the circuit, especially if one will be using electrolytic flash capacitors at ~400 volts, as electrolytics are quite intolerant of reversal.

I'm happy with magnetizing up to 20 or 25 speakers a day.

You won't be worrying the Chinese.

Steingroever is German: MAGNET-PHYSIK Dr. Steingroever GmbH: MPS Hompage EN

[Mike Sulzer]

It also saves the capacitors from degradation from reverse currents while the tank resonates. This is a big advantage of the circuit, especially if one will be using electrolytic flash capacitors at ~400 volts, as electrolytics are quite intolerant of reversal.



You won't be worrying the Chinese.

Steingroever is German: MAGNET-PHYSIK Dr. Steingroever GmbH: MPS Hompage EN

If the LC does oscillate, wouldn't the simple circuit tend to demagnetize the just magnetized device since the current flows in the reverse direction? That is, perhaps the simple circuit works because the Q is low enough so that the reverse current is a fraction of the initial forward current and so has little effect. The small amount of reverse current still might be enough to damage the capacitors, requiring the use of the diodes. If the Q is that low, then the circuit cannot save much energy since it is mostly gone before the reverse current occurs.