3.5" DSDD disks mostly bad

[Jules Richardson]

Dave Dunfield wrote:
>>> How does an entire lot go bad?  Are you seeing an exorbitant amount of
>>> bad sectors after a format?
>> The most handy machine for testing these is a Linux box.  Since these were
>> previously used on an Amiga, I need to do a low-level format before using
>> mformat.  Here's the typical response:
>>
>> # fdformat /dev/fd0u720
>> Double-sided, 80 tracks, 9 sec/track. Total capacity 720 kB.
>> Formatting ... done
>> Verifying ... Problem reading cylinder 62, expected 9216, read 2048
>>
>> These disks were found in a box, not protected very well from dust.  That
>> might have done it.
> 
> Is the drive (heads) clean? Try giving the drive a good cleaning before you
> chuck the disks.

...and if that doesn't help it's perhaps worth pulling the drive and checking 
inside for foreign objects, just in case.

have you got other DD disks from a different batch / system that format OK 
with that drive? Or a different drive you can try to rule out any problem with 
the existing one?

cheers

Jules