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Sony 800k Floppy: heads not moving

Hello

I have a bunch of Sony MFD-51W 800k floppy drives that I'd like to put back into my Mac Plus computers so that I can sell them. Fortunately, I was able to get all their eject mechanisms working properly, thanks to James Wages' terrific instructions!

But many of the drives have the same issue: Their heads do not move from the zero position to attempt to read the disk.

I have only one drive connected to the computer at a time. If a drive works, the computer boots just fine and everything is great! 

But these drives in which the heads don't move from the zero position eventually show the "X" on the screen. 

I should point out that if I manually move the heads away from the zero position prior to turning on the computer, the heads are returned to the zero position as soon as the computer is turned on. And the drive spins up after 15 or 20 seconds, but the heads never move.

I think I have about EIGHT drives that have this same exact symptom, so if there is some way that I can get them working, that would be terrific!

It just seems like such an on/off type of situation, perhaps there's some component that's known to fail, that would cause this issue, that's easily replaced? Maybe one of the tantalum caps?

Here's a link to a video of what they do upon startup: bit.ly/3r6FT40

I should probably point out that while I usually have the bare drive sitting inside the open computer, I have attempted putting a drive in the housing and using a clip lead to connect that housing to the computer's chassis, and it still behaves exactly the same way.

I have 2 drives that work perfectly without being in the housing or anything special....just sitting there sort of inside the open computer, so I don't think it's an interference issue. Plus, the issue is so definite, it's not like they work sometimes and don't work others.

Any insight would be GREATLY appreciated!

Thanks!

Ken Newman


 





 
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