Several years ago I picked up an "as is" Widget disk from eBay. I didn't pay much, and wasn't upset when it made horrible grinding noises when powered up.
Last night I was fiddling with my Lisa again and recalled a post saying there was a glass graticule inside the drive. I wanted to see how this was arranged, so I opened up the dead disk:
You can see that the head arm is attached directly to the voice coil actuator, and the graticule is mounted in the upper right. Here is a closer picture:
If you look closely you will see a corner is chipped off of the glass. I believe that is why this drive failed... glass chunks got under the lower head and it scratched all the disk surface off. I had a peek with a fibrescope and it wasn't pretty... entire sections of the platter were ground off. In this picture you can see some of the shiny flakes spread around inside the disk:
Thanks,
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Jason Perkins
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