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800k floppy drive FROM HELL!

mloret

Well-known member
Hey guys. I have spent two days working with an 800k floppy drive and I can't seem to get it to behave properly. I won't bore you with a detailed play by play but I'll summarize what I have done:

1. Disassembled, cleaned (99 IPA) and relubed ejection mechanism
2. Cleaned heads with 99 IPA
3. Per the Dead Mac Scrolls, I repositioned the 00 Track sensor
4. When that didn't work, I replaced the 00 Track sensor and lined up with hash mark on floppy frame
5. Got the drive to initialize disks and read/write those, but will still not read disks initialized in another drive
6. Did the realignment procedure outlined in Dead Mac Scrolls, loosening, turning, and tightening the stator motor housing and trying again. Tried this many times.

I worked on realigning the drive for over an hour last night and I could still not get it to work right. When I initialize a disk in the drive, the drive will read it. The drive will also write to the disk so that means the heads are fine. However, it will not read any other known-good disks initialized in a different drive. When I put foreign disks in, the head doesn't even seek. The drive spins and it asks me if I want to initialize. :( At this point I am out of ideas. I don't own an oscilloscope, I'm doing everything by hand. Does anyone have a suggestion to get this thing to work right?
 

olePigeon

Well-known member
The fact that it reads and writes its own disks does demonstrate that it works. As per the book, "If the disk formats and mounts, it won't be readable in other drives, but at least you'll know that except for alignment, the disk drive is OK."

So you're on the right track. According to the book, your stepping motor assembly is still out of alignment. Since it's just trial and error, it may take a long time to get it fine tuned without the right equipment.

The book does give some hints, though. Look at step 25. You can try turning the motor assembly until you produce the error dialog boxes it mentions. If you get the first one, "The disk "Disk Name" needs minor repairs. Do you want to repair it?," then you're on the home stretch. Turn it the same direction just a tiny bit more until (hopefully) your reference disk mounts without errors.

If you get either of the other 2 errors, then you'll need to reverse direction on your adjustments. Hopefully you marked the original Home position, since will help you determine if you simply went the wrong direction in the first place.
 

mloret

Well-known member
Thank you for the replay. I’ll give it another shot. How much should I be turning the thing?
 

olePigeon

Well-known member
Book said "a hair." So, very little. Theoretically you should start getting those errors if it's turned too much. So I'd say maybe turn it a few millimeters, but no more. See which error pops up, then work your way back until it successfully reads your reference disk from the other floppy drive.
 

mloret

Well-known member
No matter what I do it tells me the disk is unreadable and do I want to initialize. I’m definitely only turning a hair. I wonder if I’m doing something wrong that has nothing to do with tuning the motor and that is causing the unreadable disk issue. I know it’s a good disk. I know that my other 800k drives read those disks. I have used cables with both yellow and red stripes. Who knows.
 

olePigeon

Well-known member
@mloret OK, that's one of the errors it said to look out for.

Continue until either the disk mounts or you get a dialog box stating, "This disk is damaged: Do you want to initialize it?" or "This disk is unreadable: Do you want to initialize it?"
...
If you get either dialog box (This disk is damaged or This disk is unreadable), then either you went too far, or you've been turning the stator housing the wrong way. Loosen the screws and turn the housing the other way until the disk mounts.

So you've either gone too far or the wrong direction. Try going back to the home position and turn the opposite direction.
 
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