7900A drive: 1 , Me - 1/2

From: Joe <rigdonj_at_intellistar.net>
Date: Thu Sep 9 16:39:44 1999


  Sounds more like: drive 1, you 9/10! The fact that it works tells you
that it's not a hard failure and only a contact or something of that
nature. Sounds like it may have been nothing more than an oxidized contact
and reseating it fixed the problem. That's not uncommon.

  I say use the heads like they are until they start giving your trouble.
BTW I wonder if the heads are the same as those on a 7914 or any of the
other HP drives? I've scrapped some of them and I could have gotten the
heads for nothing. I may find more of them, they're not rare by any means.

  You might try blowing it out with the blower end of a vacuum cleaner. Try
using the tapered wand on the end of the hose, that will boast the air
speed. You could use a stiff brush like a toothbrush to loosen the crud at
the same time. You may want to find something bigger than a toothbrash or
you might be there for a while.


At 07:56 PM 9/8/99 -0500, you wrote:
>The score narrows, but I can't claim a complete victory....
>Tony wrote...
>>Well, if the servo can lock the heads in both directions, then the power
>>rails are probably OK (although it can't hurt to check them). Your next
>>job (and I can't help here as I don't have the schematics) is to figure
>>out how it unloads the heads (where does it apply the unload signal, what
>>causes it, etc) and then to check through the electronics. It's not that
>I went through the schematics, concentrating on the PMR board (Power
>regulator) and Drive control board. Not in great detail, but just enough to
>get a general gist of the sequence of events and "who does what". I then
>went down and checked the disc power supply (it's a separate rackmount
>unit). Then before starting to follow traces and wires I decided to pull all
>the connections from the rest of the system to the PMR board. I was
>specifically looking for wires that had come loose, or pins that weren't
>pushed all the way in the connector, etc. Double checked that my hand
>written labels on the connectors (done before removing them) showed that all
>the connectors were back in the right place.
>Powered the drive up - heads seeked and drive ready came on. Hit the unload
>switch, and the heads immediately retracted and the brake engaged. Did this
>about 10 times in a row, every time the heads retracted nicely just like
>they're supposed to. Hummm... this leads me to one of two possible
>conclusions: A) there was just a loose connector, or B) this is a total
>co-incidence that it started working and the problem might very easily
>happen again. Now that it's working, further troubleshooting to be sure of
>the exact cause is not easy. I Know I had all the connectors pushed down
>firm and in the correct place before, but, it does work now (at least 10
>times anyway, my luck the 11th time would have been the failure).
>Followup questions:
>1) The drive innards are dusty again, must be the environment (or running
>with the covers removed didn't help I guess). What is the best way to get
>all the dust out? Canned air doesn't begin to get the dust off the plastic
>surfaces, neither does a DP-style vacuum. Any tips/tricks anyone would care
>to pass on?
>2) From the previous spin-down with the heads on the platter, the bottom
>heads are mint but the top heads now have oxide streaks on them. Cleaning
>with foam qtips and IPA doesn't budge any of it. I am loath to take out the
>top heads (removable platter) and send them out for recontouring and
>test-fly because then the drive will need to be re-aligned and I don't have
>an alignment cartridge (and probably the know-how) to realign them. This is
>only important because I have a diagnostic cartridge that I need to be able
>to read for additional cpu/disk/tape diagnostics on down the road. Is it the
>general consensus that heads in this condition are ok to use or am I setting
>myself up for a major problem. What I'm hoping is on down the road to get
>the diagnostics copied from cartridge to 1/2 tape. Then I can send the heads
>off and not bother with re-alignment (other than having to reformat my
>cartridges and lay data from tape back down. Bad idea?
>Jay West
Received on Thu Sep 09 1999 - 16:39:44 BST

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