tape drive question

From: Frank McConnell <fmc_at_reanimators.org>
Date: Mon Aug 20 05:18:21 2001

jarkko.teppo_at_er-grp.com wrote:
> Hmm, first time I read about a 7976, care to tell more :-)?

Back about 1981, HP was complacent about half-inch tape drives -- they
had their 7970E design and it was a real workhorse. But it was at best
a 9-track 1600 bpi drive, and customers' data storage and backup needs
were getting a bit large for that -- the site I worked at back then
was dealing with a 20-tape full backup, and at 13 minutes to write
each tape that meant over four hours of downtime. (And this was in
the days when one bad tape would make STORE give up, and we had
plenty of Memorex MRX IV tapes.)

So HP did a deal with Storage Technology Corporation (STC) to get an
HP-IB-attached 6250 BPI tape drive to market quickly, and this device
was sold as the HP 7976 starting in about 1983. We bought one back
then. Every six weeks it would blow a transistor on its servo board,
we would place a service call, and some lucky HP CE would come out,
replace the servo board, and stand there for a couple hours with the
drive open and a tape loop mounted, twiddling some adjustments in the
drive while watching a scope on the floor. The first guy who did this
was on the tall side and was out of the office the next day with back
trouble. The second time around they sent the new guy who found he
was the right height to do this standing upright. We saw him every
time thereafter.

Being an STC drive, it has vacuum columns. Part of the CE toolkit for
the thing was a vacuum gauge which was referred to by one of the CEs
as a "suck and blow meter", in a way which made it clear that from his
point of view these were *the* two operational modes of the drive.

The vacuum columns are lined with little glass beads that are glued
to the sides of the columns. Alcohol is a solvent for this glue, so
make sure you use Freon TF to clean the drive!

There's a small board set in its own cage under the drive. This is
the part that provides the HP-IB interface. Some numb-nuts spec'd the
cage to be a little bit too small, so another tool in the CE toolkit
is a hammer to force the boards into place.

It was picky about tapes too (especially compared to the 7970Es). HP
recommended their own tapes, which I think were re-badged Graham Epoch
480s. We wanted 3M Black Watch. Our purchasing department was of the
opinion that tape was tape, which is how we got Memorex MRX IV tapes,
and later they got us a box of BASF Endura tapes that really made us
think the Memorex tapes were good. Anyway, we continued to have
problems, and there was a finger-pointing exercise in which HP told us
many of our tapes (by this point we had got the purchasing folks to
get us Black Watch) had been scored. We pointed out that these tapes
(being for system backups) were used exclusively on one drive, the
7976. HP countered by saying we must not be cleaning the drive
properly. There was some acrimony which ended up with HP replacing
our tapes and us buying a 7978 to replace the 7976. Believe it or
not, this made everyone happy: things started working for us, and HP
didn't need to make near as many service calls out to our site.

So my take on the 7976 is that somebody should save one, that others
may learn from its mistakes.

-Frank McConnell
Received on Mon Aug 20 2001 - 05:18:21 BST