Performa 475 : Disk initialization failed because the disk is defective

[Amon_RA]

I have this weird problem with the disk drive (Sony MPF 42A) in my Performa 475...

Every time I try to initialize an HD floppy disk it fails at the verification step with ''Disk initialization failed because the disk is defective".
When I try to initialize an DD floppy disk it immediately fails with "Disk initialization failed".

The drive can read floppy disks, it even reads PC floppy disks.

I cleaned the heads of the drive, dusted it out, and tried new out of the box disks.

Is there a common failure with these drives that can be fixed?

 

[volvo242gt]

Not sure if the newer drives have a similar zero track sensor setup compared to the older auto-inject drives, but, it almost sounds like the alignment is off just enough to prevent the drive from sensing track zero on a blank floppy, but still allows it to mount a disk that was already formatted. If you use the Disk Tools disk, will the computer boot in a normal amount of time, or does it seem to boot more slowly than it should from a floppy?

 

[Amon_RA]

If you use the Disk Tools disk, will the computer boot in a normal amount of time, or does it seem to boot more slowly than it should from a floppy?

Computer will boot in a normal amount of time using the Disk Tools disk.

I ordered a new floppy drive from ebay, and.... it has exactly the same issue, so I have to conclude that the issue is not related to the drive as such...

• Reading and writing to disks initialized on my other macs (e.g. SE/30) work fine without any issues.
• Reading original disks also work without issues.
• Initializing working HD disks : ''Disk initialization failed because the disk is defective".
• Initializing working DD disks : "Disk initialization failed".
• Same issue on 7.1 and 8.1.

Not sure if it matters but I am using a full 68040 overclocked at 33MHz...

 

[irdc]

I'm having a similar issue with a stock LC 475, but in addition it also won't read formatted disks. The system otherwise functions fine (though I haven't recapped it yet, which it probably needs).

@Amon_RA Did you ever figure out what the problem was?

 

[Phipli]

I'm having a similar issue with a stock LC 475, but in addition it also won't read formatted disks. The system otherwise functions fine (though I haven't recapped it yet, which it probably needs).

@Amon_RA Did you ever figure out what the problem was?

Have you cleaned the heads?

but in addition it also won't read formatted disks.

This means it is a different issue.

 

[irdc]

Have you cleaned the heads?

I did, using a Q-tip and some IPA; didn't change anything.

The drive otherwise looks fine inside, nothing is obviously damaged. Should I be looking into the SWIM (if LC 475's even have a discrete SWIM...) instead?

 

[halkyardo]

Another thing to check out is the disk-loading mechanism - if it's dirty or even just gummed up with old grease, it can get into a state where it will appear to accept a disk just fine, but the disk is not locating fully 'home', meaning that the heads and sense switches are not making proper contact. This can result in all sorts of odd issues.

Take the drive out and with the top cover removed to expose the drive mechanism, insert a disk. It should snap down onto the spindle pretty smartly, and if you push gently on the top of the disk 'carrier', it shouldn't drop down any further. If it moves down slowly, or if it hangs up partway and needs a push to make it drop down fully, then your loading mechanism needs to be cleaned and re-lubricated. It's a good idea to do so anyway, to reduce the wear on the eject motor and gearbox.

 

[Phipli]

Sometimes people break the microswitches in the drive too. In a 1.44MB drive there should be 3, two on one side, one on the other. If I remember correctly.

Even back in the 90s we were seeing drives that people had broken the switches. If they're broken it can misread the size of the disk.

 

[irdc]

I’ve cleaned and re-greased the entire drive, and it now reliably detects every floppy I insert as 800k. Unfortunately, I’m only using 1.44M floppies. So next step is going to be to check the microswitches.

Thank you for the hints! Will keep you updated.