z0rlog wrote on 2026-01-01, 12:16:

It still sounds like PSU might be an issue here, since it’s the only component I haven’t changed in this setup.

Well you haven't also confirmed that the first suspect, the drive itself, is working. Just because the seller didn't have any returns after a hundred sales it doesn't mean that it's OK. Even statistically it's about time a bad one appears 😉

Ideas: buy another cheap drive, a used and not so shinny but tested to be working maybe. Just for having parts to experiment, you don't have to use that eventually. Find someone who still has a computer with a floppy controller to test your drive. Local forum/communities: request a working drive and/or send yours to be tested. Your PC otherwise runs fine or is it also untested? And finally really make sure you didn't duplicate any potential factor in your tests just because you didn't think it's relevant to your issue.

konc wrote on 2026-01-01, 12:59:

z0rlog wrote on 2026-01-01, 12:16:

It still sounds like PSU might be an issue here, since it’s the only component I haven’t changed in this setup.

Well you haven't also confirmed that the first suspect, the drive itself, is working. Just because the seller didn't have any returns after a hundred sales it doesn't mean that it's OK. Even statistically it's about time a bad one appears 😉

You're reading it differently as me.
I read that he did test that by buying a USB-FDC adapter.
He didn't mention buying a USB floppy drive.

z0rlog wrote on 2026-01-01, 12:16:

...
Bought a USB-to-FDC adapter, just some generic on Amazon. Connected drive to my modern PC. No issues whatsoever. Even that diskette showed no bad clusters. Connected it to retro PC and tried to boot from USB-FDD, no issues again (but obviously it’s not usable beyond boot).

Okay, drive seems to be working, having tried three cables probably tells it’s not a cable issue. ...

Well you haven't also confirmed that the first suspect, the drive itself, is working

Sorry, was not clear enough, I guess.
I have USB floppy drive (to write IMGs to floppies on my modern PC) and I have bought “USB to floppy” adapter. Which basically looks like small green PCB you connect directly to the drive (like this one: https://www.ebay.co.uk/itm/174436676973). So, ALPS in question drive definitely works with this USB adapter.

But, yeah, I guess trying an older floppy should be cheaper than buying another PSU. Thanks!

weedeewee wrote on 2026-01-01, 13:12:

You're reading it differently as me.
I read that he did test that by buying a USB-FDC adapter.
He didn't mention buying a USB floppy drive.

Say it, I read it completely wrong 😁 Of course I though it was about a USB drive to prepare the disks that are not working, and buying a whole new motherboard before checking the drive didn't make sense. But yeah, I'm the one not making sense.

Are you abolsutely sure drive is configured correctly in BIOS?

Does it have a good frame ground to the system?

You mention "checked voltage? .. do you have a multimeter?, If so check voltage while drive is being accessed and note any "wobble", source should be nice and stable.

Finally, grab my ImageDisk from "Daves Old Computers" .. it has a Test mode where you can seek tracks, read/write individual tracks, and since it doesn't use BIOS (accessed floppy controller directly), It can detect/report some problems better than BIOS/DOS do. Hopefully you can narrow down exactly what is happenind.

Also, are you SURE the drive itself doesn't used 12v - I have seen some 3.5"s which do, although many don't and I would not expect it to ever work if it does (but who knows what it might be used for - perhaps just some sort of bias) .. the 5.25" to 3.5" power adapters I've seen all move both +5 and +12 to the new connector ... why no +12? .. are you using a homemade adapter? - check voltages right at the drive connector.

DaveDDS wrote on 2026-01-01, 14:26:

Also, are you SURE the drive itself doesn't used 12v - I have seen some 3.5"s which do, although many don't and I would not expect it to ever work if it does (but who knows what it might be used for - perhaps just some sort of bias) .. the 5.25" to 3.5" power adapters I've seen all move both +5 and +12 to the new connector ... why no +12? .. are you using a homemade adapter? - check voltages right at the drive connector.

If the drive is working on a USB-FDD adapter, which does not supply 12v, is working correctly, I am certain that the 12v is not an issue.

Also, are you SURE the drive itself doesn't used 12v

Yes, 100% sure. I have opened the drive and noticed +12V pin being not connected to anything (no PCB traces, not even soldered).
And no, it’s not a homemade adapter, adapter itself has four wires.

You mention "checked voltage? .. do you have a multimeter?, If so check voltage while drive is being accessed and note any "wobble", source should be nice and stable.

Yes, checked the voltage with multimeter while it was working. No issues on that side. However, my multimeter is a very cheap one, so it’s possible that the voltage dips back and forth quickly. Unfortunately doesn’t have an oscilloscope anymore to verify.

Finally, grab my ImageDisk from "Daves Old Computers"

Thanks for the tip, will try this!

Regarding the BIOS settings, I am not completely sure they are correct. However, I have tried all the possible combinations on both motherboards I have to no avail. Seen one thread here where turning off CPU internal cache was fixing some similar issue (data error reading drive A:). But it didn’t help in my case. Wondering if anything else might be affecting floppies?

Currently I have ordered one more floppy drive, this time used from 2003, hopefully it will help.

I wonder if you have some small damage to that drive PCB, a cracked solder or perhaps the terminating resistor pack. This would explain random errors and you being able to make them go away for a time when holding the drive/cable in a specific way. Perhaps the USB adapter is more forgiving or the drive is just resting differently and it works then, but not in the PC case.

A different drive would probably be the easiest "fix" to this issue. Hunting down these random problems is very time consuming and unless you do find an obvious damage spot you can never be sure if what you did fixed it, or just temporarily made it go away. ALPS is a good brand but so was Samsung back in the '98 or so, any by 2003 their drive quality went down a lot. These late production "brand new" drives are sometimes made as cheaply as possible and have very relaxed quality control, so perhaps you got unlucky with a dud.

Given that the drive worked on usb - I doubt this is the problem, but to be safe clean the heads.

(ImageDisk has a pretty good CleanHeads function which scrubs heads back and forth while cleaning)