emu at e-bbes.com
Fri Aug 12 12:14:03 CDT 2016
On 2016-08-12 10:27, Al Kossow wrote:
> 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.
18/36 channels? Which sample rate? Resolution?
> 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.
makes sense, even as you double the amount of data ...
> 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).
So, going for the 36 track heads too?
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