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

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  • Kyle Owen
    ... Yeah, the Sharpie marks made me sad too. Depending on what the switches are made of, I may can use a light solvent, but I think a slight polishing would
    Message 1 of 91 , May 20, 2013
      On Sun, May 19, 2013 at 11:55 PM, Dave McGuire <Mcguire@...> wrote:

      Congrats on your new acquisition! That's one of my favorite machines.
      That one appears to be in pretty good shape, with the exception of
      HANDWRITING on the switch handles. WTF?! Can you remove that?

      Yeah, the Sharpie marks made me sad too. Depending on what the switches are made of, I may can use a light solvent, but I think a slight polishing would actually do a better job. Also, the top case doesn't seem to latch on. I see two plastic squares screwed into the top case, but I don't see how they'd match up to anything on the power supply side to latch the case down. Do you have some photos of that side?

      Speaking of switches, the SW handle is completely broken, and 0, 1 and 2 of the address/data switches also are touchy. 0 feels as though it's busted and can be moved horizontally, and makes bad noises when switching up and down.

      Are replacement switches as hard to find as I'd think they'd be? I'd probably need just one yellow and a couple of orange ones, if 0 and 1 are broken. Was the common failure point on these simply the handle itself, or the innards holding it to the machine?


      First, find out how long it's been since it was last powered up. If it has
      been more than a few years, you may need to give the power supply some
      attention. If it was more recent than that, then at least disconnect the
      power supply from the backplane(s) to do a voltage check first. PDP-8/e
      boards are all 7400-series TTL logic which is available pretty much anywhere,
      but you still don't want to fry one. ;)

      I can probably get a variac and bring it up nice and slow, but I know that it was certainly operational within the last 10 years. It came from Auburn University surplus in the 90s and was previously installed in the microfabrication lab as an embedded computer driving a step and repeat camera.
       

      Next, take an inventory of the boards. You can look 'em up to see what
      they are, or just post them and I (or someone) will identify them for you.
      (we'll want to know what it's got anyway! ;))

      I have a photo of the tops of all of the boards in that album, but I can take all the cards out and examine them individually.
       

      Next, you'll need to hot-wire the switch until I (or someone) can send you
      a key. You don't need to literally hot-wire it; you can just remove the
      switch mechanism from the lock and turn its shaft by hand.

      Will do! Are the keys all the same, or did each switch have its own matching key? 

      When you get that far, shoot an email back to the list and we'll go from
      there...either I, Dave G, or possibly Bill D will be able to help you out.
      (among others I'm sure!)

      And once again, congrats! The 8/e is a really nice system...I'm sure
      you'll love it!

      This has certainly been a "dream machine" for a long time. The front panels were the best, and finally getting to play with one will be a real treat. Thanks for the tips!

      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
        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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