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

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  • Kyle Owen
    ... Measuring the voltages again, I see the 5V bus is 5.12V, 15V is 15.24V, -15V is -15.12V, and V2 is 4.32V. V2 sounds pretty low...what should I check for
    Message 1 of 91 , May 26, 2013
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      On Tue, May 21, 2013 at 11:09 AM, David Gesswein <djg@...> wrote:

      Your 5V is a little higher than I would expect. It will drop some under
      loading. Also the contacts and 1/4" quick connects tend to get high
      resistance. Either clean or wiggle them under load and if the voltage changes
      give them more attention. The 5V fuse holder melting is also a known problem.
      With your lightly loaded system it should be ok.

      Measuring the voltages again, I see the 5V bus is 5.12V, 15V is 15.24V, -15V is -15.12V, and V2 is 4.32V. V2 sounds pretty low...what should I check for this bus?

      Also, what's the fix for the melting fuse holder problem? I see that there's a 10A fuse in the fuse holder, but the rating next to the holder says 25A. I'd expect a 25A fuse to have a lower resistance, yes? Would that help then?

      I also noticed that my 8/E has only one Unibus. Did they not by default come with two? Maybe that's why there's a 10A fuse?

      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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