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From: info-mac@uw-beaver
Newsgroups: fa.info-mac
Subject: Disk Surface Damage
Message-ID: <444@uw-beaver>
Date: Thu, 17-Jan-85 17:19:14 EST
Article-I.D.: uw-beave.444
Posted: Thu Jan 17 17:19:14 1985
Date-Received: Fri, 18-Jan-85 03:18:42 EST
Sender: daemon@uw-beaver
Organization: U of Washington Computer Science
Lines: 42

From: decvax!ucf-cs!peora!jer@UCB-VAX

Yesterday while deleting some old files from my most frequently-used disk,
the finder started behaving anomalously -- the icon outlines wouldn't
follow the cursor when moving the icons around, eventhough the icon moved
when the mouse button was released; when I tried to launch an application
subsequently, I got a "bomb" error code, and upon restarting, a "Sad Mac".
After booting from another disk, I inserted the disk I had been using,
and was told it was "damaged" and would have to be reinitialized; on
reinitializing, the number of blocks in the disk was much smaller than
usual, apparently the result of bad sectors.

On examining the surface of the disk, I found that the disk surface was
uniformly covered with small, comet-shaped marks.  These are about 2 or
3 millimeters long on the average, although they vary, and are extremely
narrow.  One end (the same end on all the marks) is always widest, with
the mark tapering off until it disappears at the other end.  They resemble
scratches, except that depending on the angle of the incident light, the
wide end seems irregular in shape.

I then examined some of my other disks, and found that others also have the
marks, in proportion to their frequency of use.

My question: is this a problem common to all (or many) Macs, or is it some
peculiar problem with mine?  One thought that occurred to me was the
recollection of someone in here mentioning that once after his diskette had
been spinning for several hours (due to some problem with a software product
he was beta-testing), the diskette built up a static charge which caused
a spark to jump inside the machine.  I wonder if these marks might be the
result of small static discharges?  However, I would think that such dis-
charges would tend to erase data on the disk; and also, these marks do look
more like scratches.  Any ideas as to what the problem is?

To look for these on your disks, slide back the metal cover and hold the
diskette such that the light from a lamp is reflected off of it, and rotate
the disk with respect to the light source.  The marks are most visible on
my most heavily-used disks (maybe 20 or 30 are visible at any one time
through the slot); they are hard to find on infrequently used ones, and
not present at all on unused diskettes.

					-- E. Roskos
					   jer%peora.UUCP@Berkeley