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Pickup demagnetising

#41
Its not black magic. If you get a galvanometer (some 90 USD). Some cheap pickups with Alnico mags, not ceramic. Couple of neodyme magnets and a wise (like on that video), you can manipulate the Alnico magnets amazingly easy. Really.
With a galvanometer (Tesla- or Gaussmeter) you can measure the polarity and strength. A compass is very limited for measuring the PUs.

That isn't a pro meter, but good enough.
US Stock WT10A LCD Tesla Meter Gaussmeter Surface Magnetic Field Tester | eBay


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Be aware that strong little neodyme magnets are used in some unpredictable places like toys, iPad cover closing system. They can de/remagnetize Alnico if they get close enough. Mechanical watches can get magnetized easily with neodymes and it happens instantly.
 
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#42
The worst was the old Rickenbacker horseshoe pickups … they actually had magnetized steel shoes.

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#43
You're right to worry. You should follow these rules asap:
1. Remove all metal from your bass. Instead use plastic screws or glue, plastic tuners and a wooden bridge.
2. Play with oven mitts on, keeps the iron in your blood away from the magnets.
3. Keep away from light sources: sun, lamps, and especially the moon.
4. Move to Everest. The further away from earth's core the better.

You're welcome.
 
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#44
It takes a deliberate effort or a bizarre accident to audibly demagnetize a pickup magnet that has already stabilized. They all do drift down a little bit after being fully charged initially, but they don't continue to lose power past that point unless you do it on purpose – which you certainly can do if you want to weaken a pickup, or just weaken certain pole pieces for better string-to-string volume balance (this latter technique was suggested to me by Lindy Fralin himself, in order to balance a Jazz Bass pickup).

See the Bill Lawrence mini rant on the issue. If anyone knew guitar pickups backward and forward, it was him.
 
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#46
Well, I suppose that when measuring the electrical resistance of the pickup winding you could also be either demagnetising or reinforcing the magnetisation of the pole pieces ... So it is better to choose well how to apply the ohmmeter's battery polarity, when measuring the resistance of the pickup. :eyebrow:
 
#51
byacey said:
I would call B.S. on this. Anything that was magnetized once can be re-magnetized again.
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I don't know. I read the account of someone employed at Rickenbacker at the time and was part of the team that worked on McCartney's bass when it was sent in for refurbishing. He said they sent the horseshoes out to be recharged and the word came back that they wouldn't recharge. I don't have any independent knowledge of how that went, or why it didn't work.
 
#53
Ross W. Lovell said:
You worry too much.

If you still have a cathode display TV don't park a 2 x 15" folded horn bass cabinet with 40 lbs of magnets next to your TV unless you like purple.
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Back when there was such a thing as a TV repairman, my dad had a horseshoe magnet (not the Rickenbacker kind, the Bugs Bunny kind). Being a curious kid, I wondered if it would have any effect, and I held it up to the TV screen. It didn't turn purple, but it kinda sucked half of the picture into that one little spot. I didn't know exactly what happened, but I knew I'd be in trouble for it, so I might have broke some kind of speed record turning the TV off and putting the magnet back where I found it.
 
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#55
We have magnetometers in our cell phones, if anyone wants to play with them, the Google Science Journal allows for recording of the measurements.

Quick and dirty example: ipad close to the strings, moving down to my pickups and then away and then close and then away again. I hope it does not demagnetize it...
The peaks show the stronger field of the pickup



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#56
Abner said:
The Earth itself is a giant magnet. What are you going to do now? :oops:
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This is true, but everybody knows a genuine tort pick guard cancels the geomagnetic field over the pickups protecting them from loosing their magnetic charge. Just look at how many vintage basses there are with tort pick guards that still work (i.e., both the pick guard, and the pickups still work). So that proves it.
 
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#57
Alnico magnets do discharge over time, but it’ll take several centuries before you start to notice. I work with audio gear where we use alnico - it’s tough stuff. You can demagnetized it with heat, but the plastic on your pickups will melt and/or burn ling before you hurt the alnico.

I don’t work with ceramic magnets at work, but I have had basses with ceramic magnet pickups for 30 plus years, and new basses with the same model pickups - over 30 years, no loss of output.

Just play your bass, it’s going to be fine.
 
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#58
If you put another strong magnet right up against your pickups or very close to them, and you have it lined up so that they are North facing against North, or South facing against South, and therefore you can feel a lot of force repelling your hand held magnet, trying to push it away from the pickup magnet, but you use enough force to overcome the magnetic repulsion, then you are likely to demagnetize your pickups if you hold that magnet in place against the pickup for long enough. (How long depends on how strong your hand held magnet is.)

So now that you read this, you have been warned, and as long as you don't do that, then like others have said, you probably have nothing to worry about in this lifetime.

The time to really be careful is if you are shipping a set of pickups with strong magnets. Don't stack them on top of each other in such a way that you have to force them together to overcome magnetic repulsion. Safest bet is to lay them side by side if you can.
 
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#59
farace said:
I don't know. I read the account of someone employed at Rickenbacker at the time and was part of the team that worked on McCartney's bass when it was sent in for refurbishing. He said they sent the horseshoes out to be recharged and the word came back that they wouldn't recharge. I don't have any independent knowledge of how that went, or why it didn't work.
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I would suggest they didn't know what they were doing, or they weren't using a strong enough current to magnetize the material, or maybe a case of both.
 
#60
RumbleMan3 said:
I’ve recently learned that pickups can be demagnetised. This worries me slightly.

What exactly does it take to demagnetise your pickups? I’ve got alnico magnets and I’ve heard alnico are the most prone pickups to demagnetising.

Are smaller objects like phones, screwdrivers and like objects over time going to do anything to my pickups, whether the tone changes or the output decreases? How long would it take for it to have any affect on the pickups?

Does it only apply to magnets that are bigger than my pickups? I thought the speakers in amps have magnets in them... should I be worried? I leave my bass lying next to it all the time.

It’s also directly next to my tv aswell. Does my tv have magnets that’ll demagnetise my pickups too?

As u can tell this has made me a little paranoid :roflmao:
I’d appreciate any info I can get on this subject. I don’t want to be misinformed of anything here.

Thanks
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