I am gonna suggest something dumb / radical.

It could be that the magnetic coating on these 'new old stock' disks has developed persistent domains, just from entropy.

Basically, one way of looking at the coating, is a whole bunch of teeeny tiny bar magnets stuck to the surface by string. Not fully accurate, but 'close enough'. When these aggregate/stick together, they do so in a way that takes more energy than the drive's head can produce, to flip the other way.

Subjecting the disks to very fast oscillating fields might help 'break up' such domains, revitalizing the medium.

Do you have, or can you get hold of, a magnetic bulk eraser?

Putting the bad disks through one a few times might ressurect them.

wierd_w wrote on 2024-07-14, 06:21:

I am gonna suggest something dumb / radical. […]
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I am gonna suggest something dumb / radical.

It could be that the magnetic coating on these 'new old stock' disks has developed persistent domains, just from entropy.

Basically, one way of looking at the coating, is a whole bunch of teeeny tiny bar magnets stuck to the surface by string. Not fully accurate, but 'close enough'. When these aggregate/stick together, they do so in a way that takes more energy than the drive's head can produce, to flip the other way.

Subjecting the disks to very fast oscillating fields might help 'break up' such domains, revitalizing the medium.

Do you have, or can you get hold of, a magnetic bulk eraser?

Putting the bad disks through one a few times might ressurect them.

Hi yes I’ve heard about that I’ve actually just brought a magnetic bulk eraser on eBay haven’t got it yet it’s coming from
America I’ve seen some people on YouTube have had some success with them fixing floppy’s so I will definitely give it a try

kotel wrote on 2024-07-09, 11:12:

Check the floppies for physical damage.

Hi I’ve noticed the disk that doesn’t work has a ring line on the actual media part of the disk the bit that’s black
Do you think this could be stopping it from formatting

That's usually indicative of the head being misaligned or dirty, and scraping the media.

Yes, it ruins disks. (And drive heads, if not corrected.)

5.25" floppies - rings, scratches, coating coming off?

jude1977 wrote on 2024-07-13, 13:11:

Interesting the 2 disks that the seller sent me and have formatted ok are a verbatim brand so
Maybe there better brands of disk

Verbatim is well known brand but they too made floppies for various price segments. The are the teflon-coated DataLife+ series, and there are the cheap Verex ones. I bought some very questionable Verex floppies precisely to learn how to rescue them (if possible). Spent a lot of time cleaning the dirt and mold with water and IPA, with pretty decent results.
My point here is you can't be sure how the floppies were stored so even good brand ones might be duds. It's always a bit of lottery. Sometimes it's better to buy used floppies that the seller can check before shipping.

As for rings on the media surface - some floppies can shed the magnetic material due to age and improper bonding agent used, or improper storage. This residue will stick to the head, and keep damaging the floppy further, as well as any other floppies you put in that drive. And eventually the head might catch so strong that it will get ripped off. So if you see such media damage then you need to inspect and clean the heads. Be careful with cleaning - apparently most heads get damaged not by floppies but by people trying to clean them with too much force.