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800k floppy drives - happy mac then ejects


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I've got a couple 800k drives that will spin up a known good system disk to the happy mac icon, but then eject the disk. I'm doing my testing on the one that I've recapped, cleaned, lubed, and cleaned the heads (several times), but the behaviour is the same between the two. The upper head bracket (whatever you call it) is not bent on either, so they should be making good contact with the disk. I've tried the drives on several different Pluses with the same results, and working drives work as expected on all of those same Pluses, so it doesn't appear to be a logic board or power issue.  I'm just realizing now that I haven't tried swapping cables (I don't think, at least not intentionally)...

 

The head assemblies don't move when I insert the disk. They do move back to 0 after inserting the disk if I move the assembly ahead a bit beforehand, so I know the motor is working enough to do that. I've messed a bit with track 0 positioning on the one to see if it makes a difference, but it appears that the original position was correct (found the extremes in either direction, i.e. when it just shows the 'x' icon).

 

At this point, it feels like I'm just casting around in the dark. Is there a likely cause here? It seems others in the forum have experienced this as well, but I haven't seen a solution yet.

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10 hours ago, Chopsticks said:

either the heads are not detecting the disc, perhaps a head demagnetise could be an option to explore otherwise there could be an issue with the head motor and/or the head guide rails needing a good clean and lube with something like some lithium grease 

I'm not finding much (any) info about demagnetizing heads... only floppies themselves. What's involved? (or can you point me to a resource?)

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Thanks for the gadgetuk tip - super interesting videos. Making me think I need to spend more time doing track 0 alignment as I was pretty rough with it, but also maybe give the polishing compound on the heads trick a go. I don't have a demagnetizer, haven't seen one like the one he uses, interesting that he mentions it a lot.

Edited by desertrout
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If I move the head assembly forward a bit before inserting a disk, and then insert a disk and the head assembly moves back to track 0, I assume the motor is working okay. Not definitive - only one direction - but a starting place I suppose

re: sensors -  the switches at the front of the drive? Not personally... usually just need a deoxit cleaning

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