Hello Anders -
Sorry for the delay responding - I had a couple
medical issues pop up that slowed me down a bit.
Yes, there are two photosensors on the Overland
Data Tape Drive that detect BOT/EOT conditions from the shiny reflective strip.
I checked the voltages coming out of the photo
detector thingus's and see +0.3 VDC with no strip
and +3.0VDC with the reflective strip.
That seems OK to me - but, I have no schematic.
I believe from the parts placement on the board
that the BOT/EOT signal path goes into an op-amp - probably.
Regards to the List from the Rocky MOuntains,
Jack
Hi Jack,
I believe finding the load point and
bottom-of-tape has to do with photosensors that
pick up reflected light from a lamp/photo
detector assembly in the tape path. Are you
sure the lamps are working? After that you'd
look for the reflective sticker on the tape
then perhaps scope the photo detectors.
=]
--
Anders Nelson
+1 (517) 775-6129
<http://www.erogear.com>www.erogear.com
On Thu, Oct 5, 2017 at 7:47 PM, Jack Harper via
cctalk <<mailto:cctalk@classiccmp.org>cctalk@classiccmp.org> wrote:
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:Â +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:Â 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
----------------------------------------------------------------------------------
Jack Harper, President
Secure Outcomes Inc
2942 Evergreen Parkway, Suite 300
Evergreen, Colorado 80439 USA
303.670.8375
303.670.3750 (fax)
<http://www.secureoutcomes.net>http://www.secureoutcomes.net
for Product Info.
----------------------------------------------------------------------------------
Jack Harper, President
Secure Outcomes Inc
2942 Evergreen Parkway, Suite 300
Evergreen, Colorado 80439 USA
303.670.8375
303.670.3750 (fax)
http://www.secureoutcomes.net for Product Info.
----------------------------------------------------------------------------------
Jack Harper, President
Secure Outcomes Inc
2942 Evergreen Parkway, Suite 300
Evergreen, Colorado 80439 USA
303.670.8375
303.670.3750 (fax)
http://www.secureoutcomes.net for Product Info.
