analog_programmer wrote on 2025-03-19, 19:49:
Mind that you don't hold the magnet with only one of its poles pointing to the diskette and by moving the magnet over in random directions you're actually creating non-constant magnetic field.
Yeah, but I've not actually SEEN a permanent magnet with both poles in the same place.... and most are long enough (couple mm is lots) that the "1 direction" effect will
still be present, so unless you swap poles (over the same position) faster than you are moving the magnet away... you're still going to
have more residual effect. An electromagnet on AC *does* effectively have both poles in the same and can swap them much faster than
you typically "pull it away".
Ok, the special dedicated eraser tool does work for sure, but it's proven not just by my own practice, that there's nothing wrong with using a small neodymium magnet instead.
In 99.9% of cases it won't matter - the very slight unreliability from having existing magnetic domains on the media won't affect it's ability to store/retrieve digital streams *in almost all cases*
- it will however fairly strongly affect the ability of "bad guys" to recover your "erased" data.
- having said that, it's been ()x() years since I worked in an environment where we actually worried about such things -
I only use the erasers now because I happen to have them - If I didn't, I'd probably use an electromagnet on a transformer if I wanted to
"be sure", and likely just a PM if I'm trying to see if I can recover bad media (weird ... I actually remembered what this topic was about)
Another example: In the late '90s there were a very cheap chinese double cassette ghetto blasters witch erasing "head" was actually a permanent magnet (which makes contact directly with the tape when recording). Those erasing "heads" create the specific background noise which is explained by the of the magnetic domains in one direction orientation, but it doesn't make the tape unerasable, unrecordable or with remaining excessive "hiss" after it was used again for record in cassette deck with normal electro-magnetic erasing head.
It wouldn't make media unusable - just not quite as reliable as it could be in some cases (which can be fixed with proper full erase)
- I do think a key phrase here is "very cheap Chinese" ... not always the best reference on how to properly do things.
** I personally suffer from a fairly severe curse - I *have* to know how things work! I can't use "stuff" without knowing exactly what's
going on inside - same for for processes (like magnetic recording) - I do tend to get a bit anal about "the right way to do" things ...
Dave ::: https://dunfield.themindfactory.com ::: "Daves Old Computers"->Personal