Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!cs.utexas.edu!rice!uw-beaver!milton!whit
From: whit@milton.acs.washington.edu (John Whitmore)
Newsgroups: comp.sys.mac.hardware
Subject: Re: flaky ?%*(#&%#!! FHDH
Summary: Tracks can only be rewritten, not really erased
Message-ID: <1901@milton.acs.washington.edu>
Date: 14 Feb 90 03:37:22 GMT
References: <88500007@uxh.cso.uiuc.edu>
Reply-To: whit@milton.acs.washington.edu (John Whitmore)
Organization: University of Washington, Seattle
Lines: 22

In article <88500007@uxh.cso.uiuc.edu> johnsone@uxh.cso.uiuc.edu writes:
>
>When I try to erase the disk, it spits it out and gives an "Initialization
>Failed" message or something like that.  I've tried using a bit copier (CopyII)
>to copy a "good" disk over the bad disk -- the bit copier doesn't have any
>qualms about it, but when I insert the disk afterwards, the finder can't find
>some of the files and others are "busy/locked" when they shouldn't be.
>
	The (small) write heads of the FDHD can reformat a disk, but
don't entirely ERASE the disk when they do so.  If the disk was
previously written (even with test patterns at the factory), you might
be writing atop other magnetized patterns, which results in a
confusion of magnetized traces and can cause mistracking.  
The solution to this (and the 400k and 800k drives have the same
problems sometimes) is to erase the disk.  A bulk eraser has 
saved about three out of four won't-initialize disks for me. 
	Once erased, initialize as usual.  Alas, I don't know any easily
available demagnetizers for you to use; I work in a Physics lab, and we've
got a half dozen demagnetizers to choose from (average vintage: 1950).

I am known for my brilliance,               John Whitmore
 by those who do not know me well.