Tape imaging

Al Kossow aek at bitsavers.org
Fri Aug 12 11:27:46 CDT 2016

physical is a .1 grid of square pins coming off of a flex cable to the head stack.

electrical is you supply a bias current and directly read magnetic flux with an opamp

I traced all of that out the last time I made a run at this windmill. John used an FPGA
development board with an 18 channel A/D, which also controlled modified firmware on the motor driver
and digitizes the tach pulse to get actual tape speed.

Unfortunately, he never sent me the FPGA code, so I have to come up with my own digitizer and figure
out how to drive the transport. Fortunately, it's a 9914V (vertical mount), so it isn't auto-loading.
I did get a tape to move to loadpoint from the front panel, so the mods might not be too bad. He did
send me a disassembly of the microcontroller code with the patches he made.

Reading this presentation, I think he switched to 3490 36 track heads at some point.


MANY years ago, I bought a dozen 3480s in Chicago and stripped them for the heads at my parent's
farm in Wisconsin, so I could try grafting one onto another transport if I had to. I've been unsuccessfully
trying for years to get the schematics for a 9914 or 9914V (they aren't inlcuded in the service manual).

On 8/12/16 12:29 AM, emanuel stiebler wrote:
> On 2016-08-11 20:36, Al Kossow wrote:
>> One of the highest projects I have in the queue is getting one of John's
>> M4 9914V drives with 18 track MR heads running in my new lab at CHM.
> What's the interface on the 18 track head?

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