> I am astonished, actually. Flies into the face of MY experience, big-time=
..
> Heat KILLS electronics. Period.
>=20
> --Bob A

I'm not totally surprised by the Google results, these things are always on=
 and spinning, so some of the reasons for failure go away (see below).

As to your comment on heat killing electronics - yes it does, but things wi=
ll often work at high temperatures quite happily - if they are not being te=
mperature cycled. Once up to temperature and running it will often keep run=
ning.

As do some of the methods of drive failure, a system I used to service used=
 Micropolis 45MB and 75MB drives (one of them was model number 1325 IIRC, c=
an't remember the other model number). We had a significant number of each =
of these in systems which were powered on 24/7, and operate satisfactorily =
almost forever.=20

However if the system got turned off for some reason the drive would attemp=
t to spin up, and then spin down with a failure. It was often possible to g=
et the drive to work by giving it a rotational shake on the spindle axis, a=
nd then once the drive was operational it would stay operational. We learne=
d that the trick was to do a full backup real quick and then replace the dr=
ive.

Analysis of failed drives showed that there was a flexible PCB that had the=
 head connections. This went around a plastic block that secured it at the =
body end, but the shape of the block was such that with the heads in the la=
nding zone the flexible PCB was stretched around a sharpish edge. After yea=
rs of operation the PCB would get cracks in the tracks, and the stretch aro=
und the mounting block when in the landing zone would pull the tracks apart=
 to a point where when attempting to power up again the tracks to the servo=
 head would be open circuit and the drive would power down with a 'failure =
to find servo track' error.

This was about the only failure mode we saw with these drives. I suspect th=
at many drives have a similar problem as the major failure mode, so if driv=
es are kept in operation 24/7 the failure rate can be pretty low - until yo=
u power down.


--=20
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--=20
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