All KAO-brand 128MB MO disks fail to mount (Sony disks from same era/setup work fine) — diagnostic details inside

[Tra Sakana]

Back in the mid-90s I used a Quadra 840AV with an external SCSI MO drive (exact model/SCSI ID long forgotten) running Mac OS (Kanji Talk) 7.x. I recently recovered a stack of old 128MB MO disks (ISO/IEC 10090 standard, 512B/sector) written from that same Quadra 840AV setup — a mix of Sony-brand and KAO-brand media, stored together in identical conditions (climate-controlled, low humidity) ever since.

Testing them now on a PowerBook G4 Titanium (Mac OS 9.2) with a Buffalo USB MO drive (MO-CU2):

Sony-brand disks: mount and read fine

KAO-brand disks (10+ disks, same era/setup): fail identically every time — drive spins up (audible), but the LED never blinks (no seek activity), and the disk ejects automatically after ~10 seconds. No retry clicking sound.

I also tested both on a Windows 11 PC with a different Buffalo USB MO drive (MO-CM640U2):

Sony disks: drive icon appears clearly, Windows reports "disk not readable" (expected, since it's HFS-formatted)

KAO disks: drive icon appears only faintly/intermittently, then ejects after a few seconds — same failure pattern as on the Mac

So the failure is consistent across two completely different drives/OS combinations, which suggests it's not a filesystem or drive-specific issue but something about the KAO media itself at the physical/servo level. Shutter and disk surface look visually clean, no scratches, identical to the Sony disks.

Has anyone encountered specific compatibility or degradation issues with KAO-brand 128MB MO media? Curious if there's a known manufacturing/coating characteristic that causes this kind of early "can't even get past spin-up" failure, as opposed to gradual media rot.

 

[Concorde1993]

KAO disks weren’t exactly the paragon of reliability. My mother had a whole bunch of the Mac-formatted ones when her SE SuperDrive was her main computer back in the day. Some lasted years, some worked for months, while others failed right out of the box.

The best disks were made by 3M. Never had one fail. But they were more expensive than KAO. I’d put them in the same category as Memorex and the final Maxell floppies that were made in Malaysia.