If you want to troubleshoot start from the bare minimum. It is indeed unlikely that both motherboards and three drives have the same issue.
Put a motherboard on the table, connect the absolutely minimum required. Use a different cable for the floppy, different PSU, reset BIOS etc and just try to boot from a known-working disk.
The common mistake in these efforts is to assume something is fine or can't affect anything, don't take anything for granted.

Thanks konc, I will do that

Most likely it's "something software"

Do you have another system supporting a floppy drive.
If so, I'd try moving each drive to that system and confirm that they all work!

Then I'd make a simple bootable DOS disk (I don't know about later. but at least up to XP you could
make a DOS bootable disk - if you can't make one directly, there are other ways ... let us know the system/OS)

Once you get a bootable DOS disk, see if it will boot on the problem system - then see if you can
read/write files on the floppy within DOS - this would at least let you know if the system hardware is working!

Thank you for your suggestions, I will report back

just a thought, have you tried a different floppy cable? These things have been bent and worn over a couple of decades by now

Joakim wrote on 2025-06-21, 09:42:

just a thought, have you tried a different floppy cable? These things have been bent and worn over a couple of decades by now

Yes, 3 in fact! 🤣

(Stupid question... The drive is configured correctly in the BIOS, right?)

EduBat wrote on 2025-06-21, 16:11:

(Stupid question... The drive is configured correctly in the BIOS, right?)

Well, I did look in the BIOS, but there is no really much to change re the Floppy, plus I have had the PC for years without any trouble and I have made no change to the BIOS at all. It is enabled though.

Hi, in Control Panel -> System you can put drives in MS-DOS compatibility mode.
As the name implies, it should make DOS or BIOS (16-Bit Real-Mode code) control the drives..

Edit: Checkit has a drive test, too, I think.

You are not going to believe this, the flipping thing is blinking well working again now!! I don't know what I did, nothing I was trying worked and now as if by magic it decided to work!! What the bleep!

Thank you all for your comments and help it is greatly appreciated. Vogons is the best.

Hmm.. hate it when things fix itself.. You kind of want to know what you did wrong 🤣. maybe a change of humidity? :-p

Joakim wrote on 2025-06-22, 14:23:

Hmm.. hate it when things fix itself.. You kind of want to know what you did wrong 🤣. maybe a change of humidity? :-p

🤣, yer I know. I have had this before where things just start randomly working after being broken for a while, very annoying but at the same time I'm glad It's working again.

manic232 wrote on 2025-06-22, 10:04:

You are not going to believe this, the flipping thing is blinking well working again now!! ...

Always "fun".
Perhaps the cleanings did have an effect, it just took things a while to internally recover.

While it is working, I strongly recommend you make (and test) a bootable DOS diskette as I described in my last post.
(and perhaps put ImageDisk on it) - then write protect it!

That way you will have a known working test resource in case problems resurface.

Thanks DaveDDS, that is a great idea.

Just posted this which might be on interest:

Bootable diagnostics disk

DaveDDS wrote on 2025-06-25, 02:25:

Just posted this which might be on interest:

Bootable diagnostics disk

Thanks so much for that DaveDDS, I will have a look at that and see how I get on.