1 May
1999
1 May
'99
1:50 p.m.
> Take a stack of 1 or more but not more than 5
disks and
> place them on a flat surface.
>
> Run a demagnetizer horizontally and vertically over the disks
> starting beyond the edge of the disk, crossing the disk, and then
> passing over the opposite edge.
>
> Hold the Demagnetizer about 1/4" above the disks and move it
> around clockwise and anti-clockwise several times, then while
> moving it in circles, slowly lift it up until it is about 12"
> above the disks and turn it off.
>
> The whole operation should take about 20 - 30 seconds.
This sounds like voodoo to me. There must be some
point when you are
lifting the demagnetizer away that the effects from the device are
beneficial.
The "lift it slowly away and then turn off" is an important point.
This makes sure that the media really is demagnetized. If you turn
it off while near the media, you can leave the media in a highly
magnetized state.
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.
while swirling? Are you sure its not just one of
those, or a combination
of two that really make the disk better? Is this truly making the disk
better or did the disk drive become amused watching you do all this and
then just decide to work because you made it laugh?
You can have fun with large degaussers. For those with analog watches
that aren't prized too highly, you can do some really neat tricks, such
as making the run 60 times too fast (i.e. an hour every 60 seconds) or
even making them run backwards!
Tim.
1 May
1 May
2:18 p.m.
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
11:18 p.m.
At 07:18 PM 5/1/1999 -0700, you wrote:
At 09:50 PM 5/1/99 -0400, Tim wrote:
Yesterday one of our local industries was selling off some equipment to
benefit Jr Acheivment, so I went down, found a 5 1/4" disk file with a
bunch of disks, and was told I could have it for $ 2.00. The lady on the
desk, however was determined no data could leave. I came home, returned
with a bulk tape eraser and demagnitized them on the spot.
However when I tried to format them with my trusty XT it spit them out as
"can't read track 0" on both A and B drives. I formatted the disks
successfully on a Compaq clone and a Commodore PC10, and now the XT will
read them. Any ideas?
Regards
Charlie Fox
Charles E. Fox
Chas E. Fox Video Productions
793 Argyle Rd. Windsor N8Y 3J8 Ont. Canada
email foxvideo(a)wincom.net Homepage http://www.wincom.net/foxvideo
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.
2 May
2 May
5:22 a.m.
On Sun, 2 May 1999, Charles E. Fox wrote:
Yesterday one of our local industries was selling off
some equipment to
benefit Jr Acheivment, so I went down, found a 5 1/4" disk file with a
bunch of disks, and was told I could have it for $ 2.00. The lady on the
desk, however was determined no data could leave. I came home, returned
with a bulk tape eraser and demagnitized them on the spot.
However when I tried to format them with my trusty XT it spit them out as
"can't read track 0" on both A and B drives. I formatted the disks
successfully on a Compaq clone and a Commodore PC10, and now the XT will
read them. Any ideas?
For $2 you should've slapped the lady at the desk.
Sellam Alternate e-mail: dastar(a)siconic.com
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6:01 a.m.
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10:46 a.m.
On Sun, 2 May 1999, Tony Duell wrote:
Which is, of course, a major cause of problems in reading a 360k disk that
has been over written as a 360k but in a 1.2mb drive.
- don
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.
On all drives, the erase head is _wider_ than the R/W head. That's a
simplification, as actually the R/W head erases the middle of the track,
but what matters is that the drive erases a wider track than it reads or
writes.
It has to. However carefully you make and align a drive there will be
_some_ positioning errors. And if you write a narrow track than you read,
you'll end up _always_ reading a mixture of what you've just written and
what was there before.
-tony
1 May
1 May
2:22 p.m.
On Sat, 1 May 1999 CLASSICCMP(a)trailing-edge.com wrote:
So then is that all that's really required?
This sounds
like voodoo to me. There must be some point when you are
lifting the demagnetizer away that the effects from the device are
beneficial.
The "lift it slowly away and then turn off" is an important point.
This makes sure that the media really is demagnetized. If you turn
it off while near the media, you can leave the media in a highly
magnetized state. You can have fun with large degaussers. For those
with analog watches
that aren't prized too highly, you can do some really neat tricks, such
as making the run 60 times too fast (i.e. an hour every 60 seconds) or
even making them run backwards!
I saw that trick used on MacGyver once!
Sellam Alternate e-mail: dastar(a)siconic.com
------------------------------------------------------------------------------
Don't rub the lamp if you don't want the genie to come out.
Coming this October 2-3: Vintage Computer Festival 3.0!
See http://www.vintage.org/vcf for details!
[Last web site update: 04/03/99]
9366
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ard＠p850ug1.demon.co.uk -
CLASSICCMP＠trailing-edge.com -
cmcmanis＠mcmanis.com -
dastar＠ncal.verio.com -
donm＠cts.com -
foxvideo＠wincom.net