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Degausing old floppy disks?

C

cj7hawk

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Hi, I was just wondering who else here degauses their old floppy disks to address coercivity issues with the media?

It's pretty clear some disks have been exposed to magnetic force and heat at times, that I'm guessing has occasionally exceeded the curie level, and the disks can't be reformatted - drives just don't have enough field strength.

But my old video game degauser isn't ideal... And on 3.5s there's a need to move the cover etc.

So are there any better solutions? A full disk degauser or one that's like a drive that degauses the disk so it can be reformatted again? Without the fiddliness of a hand degauser?

David
 
I used a radio shack bulk eraser for disks that have been formatted with different formats.
 
I followed Chuck's lead and used the 2 Craft Magnets from Harbor Freight (99 Cents) placed
back to back.
This magnetic disc set is ideal for projects in the home, office or classroom. The discs are made
of the highest grade of ceramic available with a natural color and ground finish. Each disc features
a pull/lift capacity of 3 lb..
  • Made of ferrite - highest grade of ceramic available
  • Natural color and ground finish
  • Pulling/lifting capability: 3 lb.
Click to expand...

They work fine for me.

Larry
 
Isn't the idea of a bulk eraser to remove any magnetic field from the media?

I don't see how that will work when using permanent magnets instead. Yes, they will erase the data as well, but leave the disk surface magnetized, and to a much higher degree than a disk drive would when writing data. I would not risk doing that, as the rotating disk could then itself magnetize steel parts inside the drive.
 
Thank you for the suggestions - and I'll read that article on a DIY degausser too. Though I probably wasn't very clear in my question - I'm not actually trying to *erase* the disks, though they do get erased.... I'm trying to degauss them. To remove any fields on the disk surface that are strong enough that the disk drive can't write them anymore.,

I find maybe 20~50% of old disks I get are usable without degausing. With degaussing, that goes up closer to 90%... Something about age and heat change the coercivity of the disk beyond what a disk drive can handle. Degaussing seems to reset it -

I was wondering what experiences others have with using a degaussing tool to fix up old disks :)
 
Timo W. said:
I don't see how that will work when using permanent magnets instead. Yes, they will erase the data as well, but leave the disk surface magnetized, and to a much higher degree than a disk drive would when writing data. I would not risk doing that, as the rotating disk could then itself magnetize steel parts inside the drive.
Click to expand...

I'm pretty sure that this is unlikely. Ferrous parts that aren't the disk head itself likely aren't close enough to the spinning disk to be magnetised by the puny magnetisation that floppy disk media is capable of.

As for the head, one of the best ways to degauss something is to subject it to alternating magnetic fields, which is what the head experiences (or actually causes) when it writes to the disk. Remember that disk encoding schemes are such that all patterns of bits that you write to the disk (even long runs of 0s or 1s) are represented by longer bit strings, and these bit strings all have lots of alternating 1s and 0s by design. Any data write will result in lots of field changes at the head, which will make it hard for the head to remain magnetised.

It would be an interesting experiment to saturate the magnetic media of a disk and to try and read the disk over and over: perhaps you could magnetise the disk head somewhat since you weren't writing anything. But completely saturated disks are pretty boring to read, and as soon as you write to them or to any other disk, I imagine that your disk head will degauss itself.

See also https://en.wikipedia.org/wiki/Degaussing#Magnetic_data_storage_media
 
I'm not trying to magnetize the disk head... It's more about whether the erase head is strong enough to erase the existing signals on a disk. As disks get older I find many can't be written to - I just get write errors and format errors... Consistent bad sectors... If I keep erasing and rewriting, sometimes it improves.

Often then, I pull the disk out and degauss it, then stick it back in the drive, and it formats up just fine. It literally goes from track 0 failure every time to no bad sectors on Greaseweasel post-degauss. So I went looking for better ways to do it, but I can't find it talked about much. I doubt I'm the only one who does it.

I know disks have problems with heat, and most old disks in Australia have been stored in garden sheds, where the heat can easily exceed 50 to 60 degrees C depending on the day and ventilation, which is well past the safe 44C for floppy disks.

I don't think read heads can me magnetised.... It's on a small scale, but the constantly changing field would likely demagnetise them in any event I image.

If you have some disks that have been stored in a very hot place, and they don't write so well, but there's no signs of shredding try degausing them.

It's somethign I learned to do with old magnetic stripe cards to prepare them for writing with very low currents.
 
Timo W. said:
Isn't the idea of a bulk eraser to remove any magnetic field from the media?
Click to expand...
No the idea is to scramble the domain walls. Consider my PM eraser--like poles are facing one another, so the domains are being scrambled by the opposing lines of force. The thing won't work if differing poles face each other--I tried that first.
 
This is an interesting thread. I can't contribute productively but I have a question: could this same thing happen to old hard disks? Could one extend the life of a worn out MFM/RLL drive by degaussing it?
 
The main principle of "degaussing" is to repeatedly magnetize in opposite directions with gradually reducing the strength of the magnetization. I used to use a big 110VAC electromagnetic coil to demagnetize color TV picture tubes. The gradual reduction in magnetizing strength was achieved by moving the coil in circles (for uniform area coverage) while gradually backing away from the tube.
 
RWIndiana said:
This is an interesting thread. I can't contribute productively but I have a question: could this same thing happen to old hard disks? Could one extend the life of a worn out MFM/RLL drive by degaussing it?
Click to expand...
Depends on the drive. If one of the disk surfaces is a servo track, you'll end up bricking the drive. There's no practical way to restore a servo track if erased. I doubt that a bulk erase would have a positive effect in any case, as you have a stack of discs and penetration to the inner ones won't be optimal.
 
bburley said:
The main principle of "degaussing" is to repeatedly magnetize in opposite directions with gradually reducing the strength of the magnetization. I used to use a big 110VAC electromagnetic coil to demagnetize color TV picture tubes. The gradual reduction in magnetizing strength was achieved by moving the coil in circles (for uniform area coverage) while gradually backing away from the tube.
Click to expand...
The point is not really in demagnetizing the mediia, per se, but rather moving to a linear area on the magnetization curve. Floppy disks and, for that matter most other computer media use saturation magnetization; audio and video tape use the linear region on the magnetization curve.
 
I've got disks that I purchased that I *think were used for a mac. I've tried degauss erasing them and they will format fine. I can write to them fine using the drive that formatted (T1100 plus 720K), but the minute I try to write them in a 1.44MB USB drive, they will not read on the T1100 plus drive. It is particular to this set of disks I got from one place. I have many other 720K disks that I can format on the T1100, take to the usb 1.44MB, write anything I want to them, and then take them back to the T1100 and they will read just fine. Any thoughts on this odd issue?
 
vwestlife said:
I have had floppy disks that formatted with bad sectors, which then magically disappeared after erasing them with a bulk tape eraser.
Click to expand...
Ssme here. That claim is why i decided to buy a radio shack eraser. I have boxes of used floppies and many were giving me trouble. Its not a cure all but id say out of 3 or 4 disks giving me track 0 errors and not being able to format id at least be able to bring one back just fine. And that afds up toalot of disks.
 
VERAULT said:
Ssme here. That claim is why i decided to buy a radio shack eraser. I have boxes of used floppies and many were giving me trouble. Its not a cure all but id say out of 3 or 4 disks giving me track 0 errors and not being able to format id at least be able to bring one back just fine. And that afds up toalot of disks.
Click to expand...


This is the effect I'm talking about - a disk seems to get these "spots" that are bad sectors no matter how many times you format it, even across different drives. Sometimes they are only found during a reformat - eg, the data itself is OK but when you go to rewrite it, it's never going to format again. Especially old disks, and those that have been subject to heat.

Then a degaus, and suddenly they format OK. No bad sectors.

What does a radio shack dagauser look like? I just use a small degausing wand like used to be used for CRT degausing of video games. But I imagine there are better solutions.

Something on the smaller side of the Philadephia Experiment would be nice :)
 
If you're looking at using the RS mixmaster-type degausser for 100 floppies, be aware that it runs hot and has a thermal cutout. I believe that the instructions advise one to use it for no more than a minute at a time.
 
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