7900A drive: 1 , Me - 0

From: Jay West <jlwest_at_tseinc.com>
Date: Tue Sep 7 22:15:24 1999

Here's another installment in the ongoing HP7900A drive saga (yes, it's a
plea for advice and/or sympathy <grin>)

Installed new (refurbed) lower heads and new lower platter. Recleaned inside
of drive. Powered up, put in new removable cartridge. Hit load switch and
waited 25 seconds, then hit unload. Did this a few times (the blowers and
drive spins up, but the heads don't load for 30 seconds - did this to get
any remaining particles out). Removed cartridge, powered down, removed
covers and reinspected everything inside. All looked well (including heads,
which were fully retracted).

So, this time I powered up and hit load. Waited 30 seconds, heard the heads
move out to cylinder 0. Ran drive like this for about 3 minutes, no problem.
Hit unload. When I removed the removable cartridge, I noticed the heads
weren't quite retracted all the way. They were well off the media, but not
all the way back home (the heads weren't touching each other, but they were
close). Manually pushed the heads back, rechecked everything I could find.
Repowered up the drive, after 30 seconds the heads loaded. Drive ready lite
comes on and ran for about 15 minutes. No HDI sounds at all. I was elated.
Hit unload, and after about 20 seconds heard very soft HDI. This time I left
the cartridge in, powered everything off, removed the covers, and this time
the heads weren't retracted at all. They were sitting right on the media.
Strange thing is, there's no marks on the media, the lower heads I replaced
look pristine, and the upper heads have only the very slightest indication
of oxide.

Gee - perhaps this is why the drive originally had a head crash before I got
it? I've been through the "theory of operation" text and flowcharts. Several
things confuse me. First, I thought that hitting the unload switch was
pretty much of an immediate voice coil retraction - I didn't think this went
through all the normal logic circuits. Second, the coil can't be completely
shot I wouldn't think, because as I understand it the drive ready light
won't even come on unless the positioner moves out to cyl 0 correctly.
Before I replaced the heads and media, I don't THINK I had this problem, I
think I would have noticed if the heads weren't retracting before. But, I
can't imagine that anything I did related to replacing the lower head set
and the lower platter would have anything to do with this. Input anyone?????


Jay West
Received on Tue Sep 07 1999 - 22:15:24 BST

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