(Classic Computers) HP 7970 1/2" 9-Track Reel-to-Reel Tape Drive

Jack Harper harper at secureoutcomes.net
Thu Oct 5 18:47:04 CDT 2017

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,


At 12:22 AM 10/4/2017, Curious Marc wrote:
>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:
>(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.
>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

Jack Harper, President
Secure Outcomes Inc
2942 Evergreen Parkway, Suite 300
Evergreen, Colorado 80439 USA

303.670.3750 (fax)

http://www.secureoutcomes.net for Product Info. 

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