Fun with degaussers

From: Chuck McManis <cmcmanis_at_mcmanis.com>
Date: Sat May 1 21:18:31 1999

At 09:50 PM 5/1/99 -0400, Tim wrote:
>That said, 12 (or even 6) is way too many errors for a floppy disk.
>Cleaning the heads, re-aligning, or buying new media (there are lots
>of places that still sell 8" floppies) may be the real solution.

The issue isn't with the disk I don't believe (I don't have an alignment
disk to prove it so I can't be sure). The goal of demagnetizing is to
recreate a uniform state of non-magnetism on the media.

I remember that Jerry Pournelle used to toss disks that were no longer
needed but couldn't be given away directly (because they had commercial
software on them) into a bin with a couple of those huge "fishing" magnets.
Once treated in this way they were not readable, and not usable until
demagnetized. At the time it was explained that the erase heads write a
narrower path than the read heads scan so if the track has been magnetized
on the outside it can interfere with the reading and writing of a block.
Then again, it could all be hogwash, but using the demagnetizer on the
disks did the trick. Other empirical evidence was accumulated when the
demagnetizer shut itself off while I was using it near the disk, (thermal
shutdown to prevent meltdown I guess). That disk was unusable until the
demagnetizer reset and I could use it more carefully.

--Chuck
Received on Sat May 01 1999 - 21:18:31 BST