How to degauss

[Jacew]

Re: How to degauss

I'm reviving this thread because I think there's plenty of interesting stuff non-answered about degaussing etc..

1) If/when you recharge a magnet by a stronger one, like that neodymium, does they have a "full potential" where it gets quickly and that's it, or is the magnet charge more volatile when affected by outside field?

2) Can you degauss with same magnets, and how long would it take to get same effect than that 30 sec with A8 for instance. Minutes? days? weeks?

3) Are SD standard, non-antique single coil / humbucker magnets generally fully charged? Do you know models that aren't?

[eclecticsynergy]

Re: How to degauss

I'm not an expert but this is my understanding:

1) When recharged, the magnetism will remain stable. But AFAIK recharging via a neo magnet is not able to charge a magnet as fully as new.

2) AFAIK it takes a substantially stronger charge to degauss even a weak alnico like A2. It requires an A8 in direct contact (or very close), or else a neo.

3) The only Duncans I know of that come with degaussed magnets are the Antiquities and a couple of CustomShop pickups like the Brobucker.

[Cobra1957]

Re: How to degauss

Following

[Jacew]

Re: How to degauss

I'm not an expert but this is my understanding:

1) When recharged, the magnetism will remain stable. But AFAIK recharging via a neo magnet is not able to charge a magnet as fully as new.

2) AFAIK it takes a substantially stronger charge to degauss even a weak alnico like A2. It requires an A8 in direct contact (or very close), or else a neo.

3) The only Duncans I know of that come with degaussed magnets are the Antiquities and a couple of CustomShop pickups like the Brobucker.

So if you degauss a magnet, you can't get it back fully charged even with a neo disk? That's certainly good to know.

Do I understand 2. right, that if you take let's say two A5 mags, tie them up repelling each other and leave in a drawer for a year, they won't degauss? Would the possible effect be so small you wouldn't now the difference?

What makes the old magnets degauss usually then? Or were they just charged differently to begin with?

[Discharged]

Re: How to degauss

1) If/when you recharge a magnet by a stronger one, like that neodymium, does they have a "full potential" where it gets quickly and that's it, or is the magnet charge more volatile when affected by outside field?

Referring to mag bars and rod mags used for p'up making, the only Alnico grade that can be re-charged to full saturation, and only with the strongest N52 mag you can find, is A3. All others will hold a percentage of the theorical full-saturation charge. The only way to fully saturate all alnico mags to their fullest is with a zap charger. And those don't come cheap. OTOH, A5 rod mags charged with N52 are known to produce a very pleasing tone, specially if slightly overwound in the bridge po

2) Can you degauss with same magnets, and how long would it take to get same effect than that 30 sec with A8 for instance. Minutes? days? weeks?

The most used mag for degaussing purposes is A5. Once the A5 mag is touched by another mag, depending on the grade and/or actual charge of the one used as a "degaussing tool", the actual new level is not attained instantly, but in the course of a couple of days. Fx, and for the sake of the argument, an A5 rod @ 1055 Gauss, touched with a similar rod will go down first to 58% (600 Gauss) and will stabilize @ about 65% (680 Gauss) in that time frame. All Alnico mags are prone to degaussing by very long list of external causes, but it'll remain stable within a 3% of the stabilized degaussed charge for at least 50 years. I often do this to the g-string rod in strat p'ups to balance out that way-too-loud string in both the neck and middle p'up. The result is a lot less noticeable in the bridge, so unless I'm asked for specifically, I don't degauss it.

3) Are SD standard, non-antique single coil / humbucker magnets generally fully charged? Do you know models that aren't?

All production Duncan p'ups sold retail are sold with fully-charged magnets. Only Antiquities and a few Custom Shop ones are not, AFAIK.

/Peter

[cermag]

Re: How to degauss

Maybe i can help answer a couple of questions

[QUOTE=Jacew;4258421]I'm reviving this thread because I think there's plenty of interesting stuff non-answered about degaussing etc..

1) If/when you recharge a magnet by a stronger one, like that neodymium, does they have a "full potential" where it gets quickly and that's it, or is the magnet charge more volatile when affected by outside field?

if you recharge a magnet to full saturation, which is fully magnetised it will be at its most stable. To be honest with Alnico, its always better to heat to about 100 deg for an hour to remove the volatile fields which weaken by about 5%. The remaining magnetic field is at its most stable now. Ceramic are different, fully magnetised will remain very stable. If you only partially magnetise alnico the resulting field is more prone to faster demagnetisation.



2) Can you degauss with same magnets, and how long would it take to get same effect than that 30 sec with A8 for instance. Minutes? days? weeks?

the answer is yes/no...its all dependant on the magnet material. important to understand is the coercivity value of the magnet to degauss or Hc value if your familiar with magnet specs. Generally speaking the lower the covercivity the easier the matierial is to magnetise/demagnetise. a general rule of thumb is you need a gauss field of about 8x the coercivity value to fully magnetise a magnet. so for instance:
- Aln 5 having a value of about 650 Oe (Oersted) for its coercivity you would require a magnet or magnetiser with a field of at least 5000 gauss which is achievable with a largish neo magnet
- An Aln 5 HB magnet has a gauss level of about 750 gauss is only sufficient to very partially magnetise/demagnetise Aln 5 of same size
- The magnetisation/demagnetisation effect only takes a matter of milliseconds to perform its action
- a ceramic magnet has a value of 2000 Oe for its coercivity, thus needing a value of 16000 gauss to demagnetise and a ceramic in HB size only has about 1000 gauss (i think from memory) so will nowhere near reduce the field.

[Adieu]

Re: How to degauss

So why doesn't sitting around in parts boxes or being shipped together screw pickups up more often?

[eclecticsynergy]

Re: How to degauss

P90s have their bar mags mounted with like poles facing each other and fairly close together. Despite the repulsion, I've never known a P90 to weaken much over time, even decades-old ones containing A5 pairs. (Full disclosure, I have limited experience with A3 here, and two P90s I modded by swapping a single A8 into each have only been that way for a couple of years.) But I expect that any weakening effect would be well known by now if it were significant.

[eclecticsynergy]

Re: How to degauss

So why doesn't sitting around in parts boxes or being shipped together screw pickups up more often?

In pickups being shipped together the magnets aren't close enough to each other for it to be a problem. As for parts boxes, now that more of us have A8s and neos sitting around I suspect we might be seeing the problem a bit more often.

I keep ceramics and my only neo stuck to the fridge- far from pickups and other mags. And my A8s are in a separate envelope from the other alnicos.

[Discharged]

Re: How to degauss

In pickups being shipped together the magnets aren't close enough to each other for it to be a problem. As for parts boxes, now that more of us have A8s and neos sitting around I suspect we might be seeing the problem a bit more often.

I keep ceramics and my only neo stuck to the fridge- far from pickups and other mags. And my A8s are in a separate envelope from the other alnicos.

You can keep different magnets with no degaussing problems by sticking'em together, so the attract each other. Put the weakest in the middle. Like C8-A4-A2-A3-A5-A8. The block will behave as it was a single unit.

/Peter

[Adieu]

Re: How to degauss

You can keep different magnets with no degaussing problems by sticking'em together, so the attract each other. Put the weakest in the middle. Like C8-A4-A2-A3-A5-A8. The block will behave as it was a single unit.

/Peter

Oh....so they'll normally either stick together and do no harm, or repel each other out of effective range if loose? And as long as nothing is forcing them together, it's all good?

[eclecticsynergy]

Re: How to degauss

Oh....so they'll normally either stick together and do no harm, or repel each other out of effective range if loose? And as long as nothing is forcing them together, it's all good?

Yup. that's how most of us store them.