<story><title>Recover HD Using a Magnet</title><url>http://info.iet.unipi.it/~luigi/recover-hd/text.html</url></story><parent_chain><item><author>rgj</author><text>My anecdote:&lt;p&gt;Around 1993 I had a Commodore Amiga with an A590 external hard drive. A big enclosure that could be connected to the expansion port on the left of an Amiga 500, containing a very precious 20MB hard disk.&lt;p&gt;One day, it stopped working. I tried everything but I couldn’t get it to work. A friend offered to take a look at it so I put it in my backpack and took the train to my friend. When connected to his A500, the drive worked lime a charm.&lt;p&gt;When I drove back home in the train I wondered what would be the matter with my A500 since it apparently made my A590 hard drive fail.&lt;p&gt;However, once I got home and reconnected the drive, it worked. No problem whatsoever.&lt;p&gt;Until two days later. It failed. You know what’s going to happen, right? Took it to my friend, it worked, took it back and it worked for two more days.&lt;p&gt;Turns out that disconnecting it, putting it in my bag, walking it around for a while worked just as well.&lt;p&gt;Turns out that disconnecting it, dropping it from 5cm &amp;#x2F; 2 inches and reconnecting it, worked just as well.&lt;p&gt;Which was what I did for the next four years or so. Whenever it stopped working, I disconnected it, dropped it and reconnected it.&lt;p&gt;Always loved the look on the face of people who witnessed me starting up my Amiga.</text></item></parent_chain><comment><author>ChuckMcM</author><text>FWIW the failure mode (which was also common in drives for the SPARCStation at the time) was called &amp;quot;stiction.&amp;quot; That occurred when the drive parked the heads, after power down, into the landing zone on the platter.&lt;p&gt;At Sun we took apart a number of failed drives (which could also be recovered sometimes by giving them a sharp twist) and hunted for the root cause. The answer was that over some time the drive heads became smoother and the surface of the landing zone also became smoother. When the tiny edges of the head had been removed by this process, the surface of the head was pretty much optically smooth (very little variation) and when it landed in a part of the landing zone that was similarly smooth the surfaces would push out the air between them and become stuck just by air pressure and surface friction (stiction). The drive would not spin up until the head had lifted off the surface. The firmware issue was that head lift off was checked for so quickly that the power up of the spindle was aborted before anything happened (this was to prevent damage to the head by dragging it along the platter&amp;#x27;s landing zone). By jostling the drive you could manually cause the platters to rotate and if you found a spot that wasn&amp;#x27;t completely smooth (or if you managed to have the heads move out of the landing zone) the surface would be rough enough that the head wasn&amp;#x27;t being held down and it could lift off again.&lt;p&gt;Seagate gave us a firmware fix which basically waited longer for the heads to lift off allowing the spindle motor to move the platter a bit before giving up. Quantum (the other disk supplier) beefed up the retract solenoid and gave us firmware that would try &amp;#x27;regular&amp;#x27; retract and then &amp;#x27;heavy&amp;#x27; retract before giving up. For a pretty long time I had a Seagate drive that had been disassembled to the point of exposing the heads and platters so that the effect could be demonstrated to skeptical engineers.</text></comment>
<story><title>Recover HD Using a Magnet</title><url>http://info.iet.unipi.it/~luigi/recover-hd/text.html</url></story><parent_chain><item><author>rgj</author><text>My anecdote:&lt;p&gt;Around 1993 I had a Commodore Amiga with an A590 external hard drive. A big enclosure that could be connected to the expansion port on the left of an Amiga 500, containing a very precious 20MB hard disk.&lt;p&gt;One day, it stopped working. I tried everything but I couldn’t get it to work. A friend offered to take a look at it so I put it in my backpack and took the train to my friend. When connected to his A500, the drive worked lime a charm.&lt;p&gt;When I drove back home in the train I wondered what would be the matter with my A500 since it apparently made my A590 hard drive fail.&lt;p&gt;However, once I got home and reconnected the drive, it worked. No problem whatsoever.&lt;p&gt;Until two days later. It failed. You know what’s going to happen, right? Took it to my friend, it worked, took it back and it worked for two more days.&lt;p&gt;Turns out that disconnecting it, putting it in my bag, walking it around for a while worked just as well.&lt;p&gt;Turns out that disconnecting it, dropping it from 5cm &amp;#x2F; 2 inches and reconnecting it, worked just as well.&lt;p&gt;Which was what I did for the next four years or so. Whenever it stopped working, I disconnected it, dropped it and reconnected it.&lt;p&gt;Always loved the look on the face of people who witnessed me starting up my Amiga.</text></item></parent_chain><comment><author>jacobush</author><text>The manual (or some kind of leaflet with it) of the MFM 10 megabyte drive of an IBM XT even mentioned, that the drive could seize up if the bolts were too tightly or unevenly tightened. Sure enough, I had to adjust them one fine day.</text></comment>