Message: 26
Date: Wed, 25 Nov 2009 21:18:13 +0000 (GMT)
From: ard at p850ug1.demon.co.uk (Tony Duell)
Subject: Re: Cleaning packs
To: cctalk at
classiccmp.org
Message-ID: <m1NDPFl-000J3yC at p850ug1>
Content-Type: text/plain
On Nov 24, 2009, at 1:08 PM, geoffrey oltmans wrote:
Dumb question (perhaps), but do the relative
positions of the disk
platters in the pack matter on these systems? I suppose it might for
interleaving purposes for data already recorded.
I would suspect yes but never having cleaned multi-platter packs, I'd
only do that on packs that I don't care about the data (ie I'm going
to format the pack as soon as it's "clean"). If I care about the data
that *might* be on them I probably wouldn't disassemble (ie de-stack)
the pack.
I would be very careful about dismantling the pack for another reason.
Often there is no automatic centring of the platters. If you seprate
them, you will have to centre them up. On the (crashed) 5-platter pack I
dismantled about 25 years ago (for interest), there were holes throuch
the top and bottom hparts of the hub through which you put long rods to
keep the platters and spacers _approximately_ cententerd. But then, I
think, you have to put the hu on the drive spindle (or a similar spindle
in a test rig) nd use a dial gauge to position the platters so there's
no run-out when you rotate the stack by hand. Given that moving one
platter is likely to slightly move all the others, this is a long and
tedious job.
-tony
I would not clean any pack that had a lubricated disk surface. The good
news is I am pretty sure that lubrication was introduced with the IBM 3340
(Winchester) so the 2315, 2316, 3336, 3336-11, SMD and their DEC equivalents
(RP0x, etc) were not lubricated. I don't know anything about the later
uniquely DEC packs but I expect they used high load heads and were not
lubricated.
As I recall we cleaned non-lubricated disk packs with a tongue depressor, a
non shedding wipe (Kim Wipe) and isopropyl alcohol (medical grade). You
want to make sure there is no residue!
If you don't care about the data you can disassemble and reassemble disk
packs that do not use a track following servo systems, that is 2316 and
2x2316 types. You do not have to center them up!
If you are real careful you can disassemble and reassemble a servo type disk
pack so long as you are very, very careful not to move (or replace) the disk
containing the servo pattern! This applies to the 3330 and SMD type of disk
packs. A while ago, I was surprised to find out that several "recovery"
houses were doing this routinely and claiming to recover data on the
original disks still in the pack!. If you do move the servo disk, as
witnessed by repeatable runout in the servo system, I am told that some
skilled folks can actually center them up by careful instrumentation,
measurement and gentle tapping of the servo disk in a not fully tightened
assembly.
Tom