[Coco] resurrecting 5" disks

[Robert Gault]

Bob Devries wrote:
> In the process of trying to make images of my Colour Computer disks, I 
> have found quite a few which howl when put into a disk drive. Even some 
> disks which have been carefully stored, seem to have accumulated a 
> deposit on the surface of the magnetic media.
> 
> I know there are others who are trying to do this; what method has been 
> used to clean up and read those disks, and what success rate has been 
> achieved?
> 
> I have carefully wiped the disk surface with a moist soft cloth, and 
> allowed the disk to dry before trying to read it again, with some degree 
> of success.
> 
> How have other people fared?
> 
> -- 

Your symptoms exactly match a disk that was stored under pressure. The 
result of the pressure is that the edges of the jacket flatten out and 
the internal "wipe" sheets press on the magnetic media creating much too 
much friction during a spin.

!!!!IF THE FRICTION IS NOT REMOVED, THE MEDIA WILL BECOME PERMANENTLY 
DAMAGED FROM WEAR AND HEAT!!!!

I have made many disks with this condition readable by breaking the heat 
seals located around three of the edges and reverse bending the three 
edges so that the crimping action is relieved. This is often sufficient 
to let the disk spin normally. If not, the final front edge must be 
given the same treatment. That means slipping the media out of the 
jacket and bending the front edge of the jacket. MAKE ABSOLUTELY CERTAIN 
NOT TO FLIP THE DISK RELATIVE TO THE JACKET DURING THIS PROCESS!

Once the jacket edges have been spread, there won't be any squeal when 
the disk turns in the drive. This will also be indicated by the disk now 
slipping freely within the jacket when you insert your fingers in the 
central hole. With bad jackets, the disk will barely move.

There is no need to reseal the jacket edges to use the disk. It may be 
necessary to gently squeeze the edges to get the disk in a drive. Don't 
use excessive force or the initial bad condition will be re-established.