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Re: [Altair Computer Club] Altair 680 Memory Debug

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  • Grant Stockly
    ... No. Its really strange though that VTL could use the first 2k of the card but basic couldn t even get to the MEMORY SIZE prompt. Now the things works
    Message 1 of 6 , Jul 8, 2007
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      At 12:50 PM 7/7/2007, you wrote:

      >I'd suspect bad caps. Did you try alternating AA/55 ?
      >
      >(s) Derek

      No. Its really strange though that VTL could use the first 2k of the card
      but basic couldn't even get to the "MEMORY SIZE" prompt.

      Now the things works perfectly. It just booted twice in with 10858 bytes free.
    • Steve
      This is sounding like it s most likely bad solder joints somwhere. I m not trying to insult you with these questions, but they must be asked: Are you using a
      Message 2 of 6 , Jul 8, 2007
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        This is sounding like it's most likely bad solder joints somwhere.
        I'm not trying to insult you with these questions, but they must be
        asked: Are you using a decent soldering station and solder, or
        cheesy Radio Shack products? Have you examined every solder joint
        under a magnifier?

        Sometimes a good scrubbin' on the solder side of the board(s) with a
        stiff brush will dislodge an all-but-invisible solder splash or wire
        whisker that's in the wrong spot. Also, sometimes a heat gun and a
        can of freeze spray will yield fast results.

        I have seen a surprising number of Altair problems that were caused
        by conductive stuff (wire snips, solder, staples, ...) that had
        fallen into the mother board's 100-pin sockets.

        Steve
        =========================

        --- In altaircomputerclub@yahoogroups.com, Grant Stockly <grant@...>
        wrote:
        >
        > At 12:50 PM 7/7/2007, you wrote:
        >
        > >I'd suspect bad caps. Did you try alternating AA/55 ?
        > >
        > >(s) Derek
        >
        > No. Its really strange though that VTL could use the first 2k of
        the card
        > but basic couldn't even get to the "MEMORY SIZE" prompt.
        >
        > Now the things works perfectly. It just booted twice in with 10858
        bytes free.
        >
      • Dan
        I know I should have some 680 code listing around here in my notebooks for ram testing. But I guess you have it fixed already. That link to the SWTPC site is a
        Message 3 of 6 , Jul 8, 2007
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          I know I should have some 680 code listing around here in my notebooks
          for ram testing.
          But I guess you have it fixed already.
          That link to the SWTPC site is a good reference, not much to alter to
          get it running on the 680
          Basically, the usual 00's, FF's, 'walking 1's', 'walking 0's', 'addr in
          addr' tests should help.
          You also like to have to them run multiple passes to find any flakey bits.

          =Dan



          [ vintage electrons are just as good ]
          [ http://ragooman.home.comcast.net/ ]



          Grant Stockly wrote:
          >
          > Well, my hardware problems continue...
          >
          > I can't boot basic any more.
          >
          > I have 4 16k memory boards for the Altair 680 on loan from Tom, and I'm
          > supposed to fix them.
          >
          > ONE of the boards worked perfectly... The rest have known issues. I tried
          > booting basic and no matter what it crashes when ever I try to J 0000
          > (after loading, jump to the beginning and run).
          >
          > I've done a 01, 02, 04, 08, 10, 20, 40, 80 test on all 4 banks. There are
          > no missing or stuck bits. This leads me to think that maybe one of the
          > chips has a problem half way through.
          >
          > I installed one of the bad memory boards and was able to boot basic once,
          > but the last 4k was "missing" because of broken pins. So I know the
          > computer works!
          >
          > Just for fun I loaded VTL onto the 16k memory board and ran a program
          > called "Life" which requires 2k of memory. Not a single problem. So the
          > first 4k is probably good.
          >
          > I'm going to look into a memory test program. Does anyone have something
          > like this for the 680? Something that loads 00 - FF into each address and
          > makes sure it came out right?
          >
          > Grant
          >
          >
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