Re: Copying what I can from bit rotted disks?

["Michael J. Mahon" <mjmahon@aol.com>]

Jayson Smith wrote:
> Hi,
>
>      I just discovered a bit more information. The files that are unreadable 
> seem to be on the innermost tracks on both sides of the disk. I can tell by 
> the distance the head travels as it recalibrates after a read error. I have 
> taken the step of copying off all files that can be copied without errors 
> onto a good disk, and imaging that. Are there any disk cleaning procedures 
> that might let the data be read again, or is it more likely to just be a 
> defect in the magnetic material on the innermost tracks? The errors happen 
> on two different drives hooked up to the same system.

The inner tracks are recorded at higher density than the outer tracks
(smaller circumference), so margins are tighter there.

In my experience, a hard magnetic fault has always been visible, but
I realize that does you no good.  The fact that both sides of the disk
have errors in the same region suggests the possiblity that the media
is creased or wrinkled near the middle.  On a couple of occasions, I've
been able to read creased disks by 1) carefully flattening the crease by
delicate bending in the opposite direction, or 2) momentarily increasing
the pressure exerted by the pressure pad by pressing on it with a pencil
eraser.  Both methods are primitive, but worked.  (I should also mention
that a couple of other disks with similar creases didn't work, so it's
a bit of a roll of the dice.)

Perhaps you could have someone take a close look through the window
as the media is rotated to see if there are any visible creases?

-michael

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