Marc -
I certainly do know you from your great YouTube videos.
Because of the video on the Overland Data drive, I bought one of
those that popped up on eBay, but it will not find load point.
The output voltages from the BOT sensor look, I think, good or at
least reasonable: +0.3VDC for the DARK condition and +3.0VDC for the
LIGHT condition.
The drive failed all of the power-on diagnostics when I first got it,
but I discovered how to re-initialize NOVRAM to "factory settings" by
weird button pushes - Did that and all was well.
However, the drive will not, now, find the load point and so I am stuck.
That was interesting to me as you had the exact same problem with the
7970 on your YouTube video - burned out light bulb.
I believe the problem in the Overland to be something other than the
BOT sensor.
I considered a SCSI tape drive, but really I want the classic open
reels with the classic fast/stop action. Reliving, of course, my
childhood when I grew up living inside a UNIVAC 1108 - assembly and
all that - and all those drives start/stopping :)
I consider this a long term project if I tackle it - clearly not
something that I can dash together over a weekend.
Do you think that parity issue on commands is only for the HP-IB
controller and not if I end up talking direct to the internal
controller of the 7970 tape drive?? Any idea on that?
Regards to the List,
Jack
At 12:22 AM 10/4/2017, Curious Marc wrote:
Jack,
You can drive an HP-IB equipped HP7970E with an old PC that has an
HP-IB card using Ansgar Kueckes HPDIR. I debugged it together with
Ansgar. The rub is that it only worked well with an ISA HP-IB card
running under Win98. The PCI HP-IB card running under XP uses a
driver that causes timing errors and it skipped some records, and I
don't think Ansgar ever bothered to fix it - we were happy enough to
have made one solution work... The commands used to read and write
from the tape are complex and tricky, and you have to get your
timing right as there is hardly a buffer in the interface (128
bytes). And there is this weird parity thing, where parity has to be
generated for commands on the HPIB bus, but not for data, or
something of that ilk. If not the tape just hangs the bus. There are
several GPIB emulators based on Arduino that should enable you to
build an interface.
You know me, I made several videos documenting the work on the 7970E tape:
<https://youtu.be/eCBxNhEzIfc?t=7m6s>https://youtu.be/eCBxNhEzIfc?t=7m6s
(tape interfaced with a PC running Ansgar HPDIR)
<https://youtu.be/5J8IbpJoeqk>https://youtu.be/5J8IbpJoeqk (shows
how I sniffed the HP-IB bus to figure out how the commands worked -
or didn't, also has a demo of sending a rewind command in the raw
via a paddled-in program)
<https://youtu.be/YS9dGYUbNd0>https://youtu.be/YS9dGYUbNd0 (showing
a demo with the tape attached to an HP-85, using an FPGA based gizmo
to take care of the on-the-fly parity generation)
<https://youtu.be/rAsLwcq4RNU>https://youtu.be/rAsLwcq4RNU (fixing a
loading fault on the tape drive)
Although I love the HP 7970E dearly and want to encourage you to try
your luck at it, that was a lot of work to get it to work on
something it wasn't meant for. You'd have a much easier time
bringing up a SCSI based tape.
Marc
Subject: (Classic Computers) HP 7970 1/2" 9-Track Reel-to-Reel Tape Drive
Question: Anyone have experience talking to a 7970 tape drive from
something other than an HP computer - something that does not have
HP-IB??? How is that usually done??
Jack Harper
Evergreen, Colorado
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Secure Outcomes Inc
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