Managed to repair the 3.5 inch drive that came with my HP vectra CS - PC 305,
This computer is an XT based system with a V30 processor, with 640kb ram, and internal RTC. My example came with 20meg MFM on an seemingly custom MFM controller card (no ROM on the card), a 360kb drive and a 1.44meg drive. The 20meg drive works pretty well, a few bad sectors, but not unexpected after so long. The 360kb drive worked fine after cleaning, but the 3.5inch 1.44meg drive didn't work.
I was previously using a different 1.44meg drive, but the floppy controller doesn't understand normal 1.44meg AT drives, and treats it as a 720kb drive.
After repairing a few other 1.44meg drives by replacing the old capacitors on them, I figured i'd give this one a crack, and what would you know, it was the capacitors all along.
I replaced the following capacitors
3 x 22uF 16V non-polarized electrolytic capacitors - changed to 3 x 22uF 50V non-Polaris
1 x 10uF 16V electrolytic capacitor - changed to 10uF 25V capacitor
1 x 4.7uF 25V electrolytic capacitor - changed to 10uF 25V capacitor
All the originals were surface mount miniature capacitors, and while they looked ok, they all measured bad using my ESR meter. I took a punt on the 4.7uF capacitor, just chucking in a larger cap and seeing how it went. The only problem is that the new 22uF caps poke out the bottom of the drive, but it really isn't a problem because it goes into a 5.25 inch bay and there is room for them to poke out.
So yeah, I now have an XT machine with a 1.44meg floppy disk drive 😀