Overland T490 cartridge tape drive and autoloader

Peter Coghlan cctalk at beyondthepale.ie
Thu Dec 9 15:20:24 CST 2021

Many years ago, a friend gave me an Overland T490 tape drive which has
some kind of autoloader attached which takes ten tapes.  I was told it
came out of a Tandem system.  The tapes are square cartridges similar
but different to a DEC TK50.  I can't find very much information about
the drive on the web but there are some hints that it might be compatible
with an IBM 3480.  It powers up nicely and the fan works and after a
short pause, a green LED illuminates.  There are only two buttons on
the front, "unload" and "format".

There are two DD50 connectors on the back.  One had a terminator plugged
into it labelled "SCSI differential".  The other had a ridiculously long
cable with DD50 plugs on it connected, lending further credence that
this is a differential (pre-LVD I expect) SCSI device.

I would like to get this drive working with my Alpha or VAX VMS systems
but I have never had any luck getting them to talk to it.  Recently,
I tried a using a DD50-HD68 cable I found somewhere to connect it to
a differential SCSI card in my Alphaserver 800 but I could not get VMS
to see the drive.  Not knowing what SCSI id the drive is likely to be
using makes it hard to know where to start looking for it.

There are no switches on the outside of the drive which could be used
to set the SCSI id so I opened it up to see if I could find any hints
inside.  I didn't see anything that looked like it could be used to
set the SCSI id inside either.  What I did find is that the interface
board had a connector labelled "SCSI differential" which had two short
lengths of ribbon cables plugged into it leading to the two DD50
connectors on the rear panel and another connector labelled
"SCSI single ended" with nothing attached.  There were also two ten way
jumper packs which were labelled "DI" and "SE" on each side.

So, not having any luck with differential so far, I tried moving the
two jumper packs from "DI" to "SE" and moving the ribbon cable to the
"SCSI single ended" socket.  I used a short, known good DD50-DD50 SCSI
cable to connect the drive to my VAX 4000-100A and replaced the
differential terminator with a known good single-ended terminator.
VMS didn't see the drive.  VMS has a utility called scsi_info which can
be used to send a SCSI inquiry command and read mode pages etc.  Trying it
against each unused SCSI id results in "device timeout" every time.  The
system disk is on the same SCSI bus before the tape drive and a SCSI
scanner can be connected after it on the bus.  Both devices work fine so
the SCSI bus cabling and termination is in good shape on both sides of
the tape drive.  I've tried moving the system disk SCSI id from 0 to 1,
changing the initiator SCSI id from 6 to 7 and replacing the scanner with
a terminator in case there is any sort of SCSI id conflict but scsi_info
still doesn't show up anything that could be the tape drive.

Does anyone have any information about this drive, particularly
whether it should behave like a standard SCSI tape drive and what
SCSI id and/or lun it is expected to use or if there is some trick
required to get it to start talking? Maybe it doesn't like SCSI
inquiry commands?

Extra bonus points awarded for details on how to control the autoloader.

Maybe I did some damage to it when I was trying to get it to work when
I first got it?

Peter Coghlan.

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