Floppy drive(s) repair ?

[Fraggle1]

Hi all,
this is a strange one. Today I tested three A1200s that I've been storing, and NONE of them can read or write to a floppy disk.
 
They have been stored in plastic bags, in dry, clean conditions, for about 12 months.

On inserting a floppy disk, I get the "df0:" message below the icon, and if I try to format a disk, the drives chug away for a moment, then I get the message "cannot write sector 0" (I think that's what it said)
Strangely, this also happens with an external drive that I connected to them.

I can't believe that all 3 drives, and the external unit have failed, as they were all working perfectly when they were stored.

Has anyone seen this happen before ? and if so, can anything be done ?

[Fraggle1]

yes, of course. I tried a random selection on all 3 machines. The floppies that I used are all readable on my other machines, which are in regular use.

As you can tell from my post, all the machines boot fine from HD, and appear to have no issues, so the problem can only be with the floppy hardware. Is it possible that the heads have become de-magnetised ? or might they just have become coated with particles from the air ? (anything magnetic is bound to attract some dirt)

Now if I can only find my cleaning disk.....