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Re: [midatlanticretro] Acquired a PDP-8/E

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  • Kyle Owen
    ... The three handles with broken pins have now been drilled out and replaced with part of a nail, slightly smaller in diameter than what I really want. They
    Message 1 of 91 , May 22 9:37 AM
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      On Tue, May 21, 2013 at 11:18 AM, David Gesswein <djg@...> wrote:
       

      Yes, most were only broken on one side. 

      The three handles with broken pins have now been drilled out and replaced with part of a nail, slightly smaller in diameter than what I really want. They are slightly loose on the broken side now, but they are functional. At least I can always drill larger when I find the right material to make a better pin.

      What's the preferred way to remove and replace the handles? I found the replacement part to be very challenging, particularly when there are handles to either side.

      Yes they are injection molded. The company that owns the mold would make
      more but only if the volume was enough to be worth while. The right color
      is machine specific. If you hold them near each other all my machines
      have different color handles. I don't know if it is aging or poor control
      of plastic batches.

      If there's already an injection mold available, what's holding the PDP owners from getting together and batch ordering some replacement switches? I presume this has been done at least once before, so maybe they're still running on that stock. How much might the company want for say, 100 switches of each color? Off list, could you share the contact info with the company? Also, have you been satisfied with the exactness of the replacements versus the originals?

      As far as the color difference, I'd say it's poor QC, but perhaps aging has also had some effect. I didn't notice any non-uniform discoloration, as is common with UV damage.

      Since my system is mostly operational, save most of the bulbs, I think I'm ready to test it out with some real code. I don't really know what I'm doing yet with the machine language. Where's a simple program that I can load that makes the accumulator shift left and right, or maybe just increment? I also need to study up on what the rotary switch settings do.

      Is the rotary switch supposed to turn 360 degrees, or are the stops broken? I like the fact that it's magnetic reed switch-based than normal silvered contacts. Fancy!

      Where can I find the pinout information regarding the serial interface card for RS-232 operation?

      Thanks again for everyone's help and suggestions.

      Kyle
    • Dave McGuire
      ... OS/8 needs a random-access storage device; paper tape won t do it. Magnetic tape drives are *physically* sequential-access, of course, but the TU56 (for
      Message 91 of 91 , Jun 6, 2013
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        On 06/06/2013 12:54 PM, Kyle Owen wrote:
        > That looks like a nice product, but yes, it's certainly expensive. I've got
        > some FPGA background myself, along with several different microcontrollers,
        > so I may see about creating something that will work with my high-speed paper
        > tape interface. That could be considered an OS/8 storage device, yes?

        OS/8 needs a random-access storage device; paper tape won't do it.
        Magnetic tape drives are *physically* sequential-access, of course, but the
        TU56 (for example) is logically a random-access, block-oriented device. (with
        highly variable latency ;))

        > I would
        > have no idea how to go about writing a driver for it yet, but perhaps it'd be
        > in my best interest to start reading up on the commands for the card and then
        > learn more about OS/8. Do you have any suggestions on recommended reading for
        > this?

        If this was a generally-directed question...The book you want for "most
        things OS/8" is the "OS/8 Handbook". It is excellent. Try to find a paper
        copy if you can, but it's available in PDF on bitsavers:

        http://bitsavers.trailing-edge.com/pdf/dec/pdp8/os8/OS8_Handbook_Apr1974.pdf

        -Dave

        --
        Dave McGuire, AK4HZ
        New Kensington, PA
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