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Interview with Dave Cochran from HP Labs

Discussion in 'Electronic Design' started by David L. Jones, Oct 23, 2007.

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  1. For those interested, here is a 1 hour interview with Dave Cochran
    from HP Labs, the designer of HP's first digital voltmeter and the
    early calculators including the HP 35. The interview is in honor of
    the 35th anniversary of the HP 35.

  2. John Larkin

    John Larkin Guest

    I would love to contact any surviving HP calculator designers from
    that era. I have two dead 9100's that I'll either fix (if I can find
    schematics) or toss into the dumpster (if I can't.)

  3. Andrew

    Andrew Guest

    Try contacting this site for the schematics.

    Oh they do have them for download when you use the search feature.
    Also John does acquire such beasties.

  4. Andy Wood

    Andy Wood Guest

    Now you are talking calculators! If I was foolish enough to collect
    anything, I think it would be calculators - and HP35 and HP9100 would
    be high on my list of ones to start with.

    At around $5000 when introduced, I was never going to own a HP9100.
    Heck at around $400 I was not even going to own a HP35 either, but I
    did have the chance to spend many, many hours "playing" with both of

    The 9100 weighed about 16kg but I can assure you it was portable! I
    helped somebody take one on a small boat to do some survey position
    calculations. I can still remember the other bloke as he nonchalantly
    stepped on to the boat with the borrowed 9100 under his arm, and the
    visions I had of it ending up at the bottom of the harbour. Not to
    mention the Honda generator we had to take with us to power the

    Andy Wood
  5. Tom Bruhns

    Tom Bruhns Guest

    Have you looked in the HP Journal? I'm 99% sure there is a group of
    articles about the 9100s, and there will be names of the authors, at
    least. When did they come out, about '69 or '70?

  6. Joerg

    Joerg Guest

    Are they totally dead? Sometimes it helps to hold a scope probe to a
    supply rail here or there. That'll show if it's missing somewhere or a
    cap has dried out. If not completely dead: Check the wire braid core
    connections. I have seen wire ends corroded away at the solder joints,
    maybe from flux residue (wasn't HP though). Gear from this era also had
    large crystals where the innards could fall off if bumped too hard or
    the silver on there has blackened and lost contact (scope will show
    missing clock).

    Other than that, I am sure the Russians have got the schematics ...
  7. Sarason

    Sarason Guest


    There are some schematics and service and operations manuals there.If
    you want to through it in the dumpster the owner of the website does buy
    these museum pieces.

  8. John Larkin

    John Larkin Guest

    I have the service manual, but it only includes the power supply and
    CRT schematics, none of the logic. The only schematic I've seen was
    reverse-engineered from a 9100B, very cryptic, and I have a couple of

    The HP archivist claims that she has all the schematics and, no, we
    can't see them.

    These aren't museum pieces to me. These are very cool but broken
    calculators I want to fix and use. There has *never* been a calculator
    that is as nice to use as a 9100.

  9. Joerg

    Joerg Guest

    Have you probed around in there to see if the vital signs are present?
    From my teenage days of buying at ham fests and repairing stuff I
    remember that most faults are remarkably simple. A broken trace, a bad
    relay, a burnt out diode in the PS, that sort of thing.
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