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2182Test Equipment and Circuit Debugging, was Re: surplus MSI/88e

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  • Mark Graybill
    Jun 2, 2004
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      > What's even more "hen's teeth" is a low-cost logic analyser. I've seen
      > HP
      > 1652Bs going on Ebay.com fairly cheaply, but almost all of them had "No
      > international bidders, too heavy to ship" at the bottom of the item
      > listing.
      > I saw one on ebay UK a while back - it got sold to a "breaker" -
      > someone who
      > buys working test equipment and then rips it apart. I expect the
      > boards from
      > the analyser he bought (for well over what I've seen them sell for
      > through
      > the major test equipment dealers) to appear on ebay at some point in
      > the next
      > month. *sigh*.

      It depends on what you want, and I've seen a fair few that provide
      international shipping (as well as listings from several different
      countries.) If you're willing to settle for an old 1600A, you can get a
      real bargain, and it perfectly adequate for just about any retro
      project and most AVR/PIC/etc.-type microcontroller projects.

      There's one HP 1652B logic analyser listing for the UK up on EBay now,
      I didn't look at it in detail, though.

      > An oscilloscope is useful, but totally hopeless for watching the
      > WRITE_EN
      > line and the data bus at the same time :-/
      >
      Add a 47K pulldown resistor to the /WE line for a start. My experience
      is that it's needed, whether you're using 2102's or new ICs. Without it
      there may not be a long or low enough pulse on the downstream side of
      the Memory Protect diode-OR to ensure reliable writes.

      A dual-trace storage scope won't let you watch the entire data bus, but
      you can watch one bit and /WE. Though I know it's nothing like having a
      logic analyzer.

      When I built my first Elf I thought I was in fat city because I had
      both a regular VOM as well as a digital VOM that I had added a Hold
      feature to, not to mention a buddy who had a scope, and would be
      willing to even haul it over to my place. I guess it's a good thing the
      only problem I had with my first Elf was a cold solder joint.

      -Mark G.
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