27 May
2012
27 May
'12
5:11 p.m.
On 27 May 2012 at 22:48, Mike van Bokhoven wrote:
So, my question is: is there any way he can tell
whether a particular
disk has this loose oxide problem, without running the disk in a
drive? The drives in question aren't very easy to open and clean
manually (later Unidisk plastic-case drives), and he has no cleaning
disks (though they are pretty rough on heads anyway, I hear). Perhaps
gently rubbing the disk with a cotton bud might reveal very loose
oxide without damaging the disk too much, but I doubt the disk would
release enough to discolour the bud.
A sure sign is a "squealing" or other noise when the drive is reading
a disk.
Absent that, I go by brands; I don't trust Control Data or Wabash
floppies. The budget Dysans (pink label, not purple) were terrible
also, but fortunately you don't see many of those survivng. Brown
Disk, some Radio Shack-branded disks (I suspect they were probably
from CDC) and a few others are equally bad. Read at
your own risk.
You can test a 5.25" disk for flaking by scratching the oxide near
the hub with an X-acto knife. Go easy--you can make any media flake,
but the bad stuff *really* flakes. It doesn't harm the data, since
you're completely outside of the storage area.
Beyond that, look to how the disks were stored. If they were stored
at 40C or above, expect trouble from any disk.
While most people use isoproanol to clean heads, I've found some
sticky oxide that won't come off using alcohol. For that, I
CAREFULLY use a swab moistened in perchloroethylene, being careful to
steer clear of any plastic surfaces. The old cleaning kits used
Freon TF, but unless you have an "in" with Special People, you can't
get it. Too bad, that--if commercial businesses hadn't slopped it
around by the tankerload, the "ozone hole" thing may never have
happened.
For what it's worth,
Chuck