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Servo drive signals for HP 7978 tape drive controller

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Clifford Heath

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Aug 12, 2003, 7:50:05 PM8/12/03
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I have an old HP 7978 magtape drive with two lovely servomotors
I guess about 6" diameter and 8" long. The P/S and drive hardware
is separated in the box from the control electonics, joined by a
flat ribbon cable.

To re-use the servo gear, I'd like to know what signals get sent
down that ribbon. Can anyone suggest a way of finding out (that
doesn't involve hours with a meter and CRO)?

Clifford.

Jeff Shirley

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Aug 13, 2003, 6:09:51 PM8/13/03
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Hi Clifford.

You might be able to find a manual for the thing online somewhere, especially
if the drive is a rebadged Fujitsu, Cypher, or other common brand. I have
manuals for several 9-track drives, and they all have schematics.

I am using Fujitsu 9-track reel motors for the main drive on my robot. The
servo board was about 8x14", and contained two bipolar H-bridges built onto a
massive heatsink. I scrapped that thing, and instead use a dual MOSFET
H-bridge on a 2.5x4" card to drive them.

Jeff.
--
Jeff Shirley
no-...@mindspring.com
"Bill Gates is filthy rich, but that doesn't mean I want to be married to him."

David Collins

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Dec 28, 2020, 7:18:04 PM12/28/20
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replying to Clifford Heath, David Collins wrote:
I'm replying to your 17 year old post about your 7978 tape drive. I have one
of those that I'm trying to restore but I fear the tape head has been affected
by corrosive atmosphere. Do you still have the 7978 tape head and would you
be willing to part with to help get a museum piece up and running? THanks in
advance. David Collins

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for full context, visit https://www.polytechforum.com/robotics/servo-drive-signals-for-hp-7978-tape-drive-controller-33691-.htm


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