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First post, by Hezus

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I've got an IBM model 30 (8086) with a 720kb 3.5" floppy drive (dfl413c04a). I've seen the drive work once, but since it has not been reading any disks. So I took it apart and cleaned it, but I've hit a roadblock and I'm here for some help.

So, the head seems to read just fine, because It can determine that floppies are not bootable. But as soon as I insert a bootable disk it'll keep reading it forever. I've tried real DD floppies from the early 90's but that doesn't seem to make any difference. What does seem to be the problem is that the head is not moving forward to read the rest of the disk. I've cleaned the guiding rail and I was able to manually turn it to move the head further. When the machine initialises the drive the head moves back and forth on it own, so that's means the gears are working. But, as mentoined, it doesn't do that when a disk is inserted.

Anyone has any idea how to fix this?

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Reply 1 of 2, by Hezus

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I managed to get it to work 😁

So it turns out this was not a direct hardware problem of the FDD itself, but rather of the whole system. it seems the IBM Model 30 hardware doesn't take kindly to newer MS-DOS versions. I figured that out because (as a last hail Mary) I formated a 720 disk with the original IBM start-up disk content and suddenly it reads it just fine. I'm not sure which MS-DOS version it'll take (probably 5.0 or something), but I'll test that later.

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Reply 2 of 2, by Hezus

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Not trying to necro my own threads, but I thought this info was relevant enough to add for reference in the future. I always hate it when I search for solutions, then find some thread with someone claiming to have fixed it but not telling how to do it or what the actual issue was...

As suspected the FDD of the IBM Model 30 doesn't handle certain boot sector information, mainly any DOS version higher than 5.0. I feared that the entire system might have a problem running DOS 6.22 but I can report that this is not the case. I've installed an XT-CF Lite (v4.1) card with a 2gb compact flash card and used a bootable MS-DOS 6.22 image I found online (mirror)), which seems to run just fine. You can use WINimage or HDDrawcopy to create such an image to your CF-card.

Hope this helped a few people out there.

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