What would demagnetize a pickup?

[dlenaghan]

Hi all,

I'm in the process of replacing various bits and pieces on an old Guild JS-II I got recently, and I've gotten curious about how old passive pickups become demagnetized. I'm trying to be careful with the various bits and pieces, and I'm not too worried, just curious.

I see pickups on eBay all the time that need to be rewound for whatever reason, or pickups listed as DOA.

.. Although my curiosity is partially driven by the knowledge that replacement parts for this bass are few and far between, and somewhat pricey.

[SGD Lutherie]

The magnets in pickups don't generally demagnetize, and in fact can't unless they are in the presence of a stronger magnetic field. And the magnets in humbucking pickups like in the Guild, are touching steel keeper bars, so they are even more unlikely to become demagnetized than the rod magnets used in single coil pickups.

If a pickup is listed a dead, the coil wire is probably broken. They can be fixed by repairing or rewinding the bad coil.

[dlenaghan]

So it's safe to say that my laptop is in greater danger of my pickups than vice versa?

[mongo2]

Here's a FAQ about demagnetizing:

Demagnetizing FAQ

[bassbenj]

Originally Posted by dlenaghan

Hi all,

I'm in the process of replacing various bits and pieces on an old Guild JS-II I got recently, and I've gotten curious about how old passive pickups become demagnetized. I'm trying to be careful with the various bits and pieces, and I'm not too worried, just curious.

I see pickups on eBay all the time that need to be rewound for whatever reason, or pickups listed as DOA.

.. Although my curiosity is partially driven by the knowledge that replacement parts for this bass are few and far between, and somewhat pricey.

Pickups don't get "dead" for bad magnets. Usually it's broken wires. Magnets do loose magnetism over time. This comes from shock, vibration, temperature cycling and just plain aging. Strong magnets usually have an iron piece called a "keeper" to "short" the field to make them last longer. Pickups usually don't have keepers. And anyway the shock of snapping one on your magnets might do more damage than the keeper would prevent.

Magnets that have lost some of their power are not ruined forever. It's important to know that only the molecules have come out of alignment. So if you have some rare vintage pickup with a weak magnet, all you need to do (easier said than done, sometimes) is remove the magnet and and send it to a place that can re-energize it. It's pulsed gadget that impresses a short term but very strong magnetic field on the magnet to restore it's magnetic power.

[SGD Lutherie]

Originally Posted by bassbenj

Pickups don't get "dead" for bad magnets. Usually it's broken wires. Magnets do loose magnetism over time. This comes from shock, vibration, temperature cycling and just plain aging. Strong magnets usually have an iron piece called a "keeper" to "short" the field to make them last longer. Pickups usually don't have keepers. And anyway the shock of snapping one on your magnets might do more damage than the keeper would prevent.

Correct. But read what I wrote in post #2. Humbuckers do indeed have a keeper of sorts; there is a steel bat that the pole screws are attached to. Also because it is a short magnetic loop above the pickup, the magnets keep their charge.

Magnets don't really age much in pickups. Old pickups do often sound different, but if you measure the Gauss readings on some, you will see that the magnets did not weaken.

Magnets that have lost some of their power are not ruined forever. It's important to know that only the molecules have come out of alignment. So if you have some rare vintage pickup with a weak magnet, all you need to do (easier said than done, sometimes) is remove the magnet and and send it to a place that can re-energize it. It's pulsed gadget that impresses a short term but very strong magnetic field on the magnet to restore it's magnetic power.

You can also recharge weak magnets with strong neo magnets and a fixture to hold the neos. Usually that involves a metal vice.



Also in this case, these are very dark sounding pickups, so a slightly weak magnet wont matter much.