Date   : Mon, 26 Sep 2005 00:46:32 +0200
From   : "W.Scholten" <whs@...>
Subject: Bad floppy disks (Re: Floppy Drive Problem)

Peter Bilt wrote:

> I have a new Watford Electronics dual floppy drive used on a master for 
> my model b. Opened the drive case and the drive looked a1 inside, as 
> new. As soon as I fired it up it worked like a dream, after a couple of 
> days problem free use I am getting errors on both drives.
>  
> Soon after the errors first appeared, I could hear high pitch squeel 
> when the disk is spinning. This would go after a minute or so, and the 
> drive would be ok for a while.

   high pitched whine => junk on the drive heads from degenerating disk 
surfaces. This may or may not be removed by using (reading/cataloguing) 
other disks. If not, you'll have to clean the heads with alcohol. I've 
had to use a (abrasive) head cleaning disk to get my drives working 
again some time ago. As a result of my experiences, I will never again 
put Control data/Storage master media disks into my drives.

See:
   http://8-bit.summerfield-technology.co.uk/varia/durability.html

A few more details I've not yet written up elsewhere:
  - The page "recovering data from improperly stored floppy disks"

      http://www.swtpc.com/knowledgebase/kbpage1.htm

    was previously mentioned on this list. It mentions mold causing 
degeneration. I'm not sure this is really the case, in the cases I 
experienced this is definately not so: The disk surface was degenerated 
but there was no trace of mold. In fact, I can usually only see the 
degeneration of the surface by breathing on it, if the surface remains 
evenly coloured, then it's ok. If some parts get darker than others, 
then there's a problem. This has happened to disks that I know have been 
properly stored, so no mold. Furthermore, other disks from the same 
source were ok. perhaps natural degradation similar to what happens with 
plastic cables (the weakmaker (not sure if this is the correct english 
term, but this is the stuff that made the plastic pliable) eeks out of 
the cable. This is the stuff that eats into styrofoam and even some 
types of plastic casing).


   This page further mentioned something that I completely disagree 
with: using alcohol on spotted disks to read and copy them. This is very 
very very very bad because alcohol is a degreaser and will exacerbate 
the problem. Some type of grease/fat would be better. Not sure what's 
best yet, but I've tried for example using skin grease. This worked 
perfectly, no whine, disk was read perfectly.

   Note that the same degeneration also occurs on tapes. You can see the 
uneven colouring (but no mold) directly on some, on others breathing on 
the tape with show the decay.

  Early Acornsoft disks are among the worst, many are bad, and some were 
destroyed when I tried to read them. The surface was soft on these 
disks, completey unlike good disks. This stuff scraped off, stuck on the 
drive head and then cut a groove in the same disk. Disk was thus 
nuked... Trying to format/read a good new disk (onto which I wanted to 
copy the original) cut a groove on that too. That's when I needed to use 
a head cleaning disk.

   This brings me to the final point: Exact copying of these disks. 
Which programs can handle the old Acornsoft 40/35 track format disks?

   Or has anyone got the source for a copier that handles deliberate bad 
tracks/sectors/non-standard formats so I don't need to make a program 
myself? I'd prefer a BBC program to PC stuff.


-- 
Wouter
---
BBC computer/magazine scans:
   http://8-bit.summerfield-technology.co.uk/