6961Re: Altos 5-5AD Restoration
- Feb 4, 2008Thanks Bill - always helpful to have "real world" fixit stories.
RS232 drivers are always suspect in machines of this vintage since
they are easily damaged if terminals/modems etc. are dis/mis-
They are also susceptible to electrostatic damage since they are
exposed to the outside world through serial cabling. One of my early
tech jobs as a grad student was maintaining a long serial line that
joined two buildings on campus.
After every thunderstorm, I could be almost certain that at least one
of these chips would be "blown" - often completely out of it's
socket - by induced spikes due to lighting. Terminal and computer
ends were protected by opto-isolators but the intermediate drivers
were always at risk. The problem was eventually solved by installing
fiber, but that was a "real" solution that took a bit more resources
than just stringing cable along convenient fire escapes.
--- In email@example.com, "B. Degnan" <billdeg@...>
> Altos 5-5AD board repair
> With tutoring from Bob Grieb, I learned how to better troubleshoot
> motherboard. I can again see the self test boot screen, referred toearlier
> in this thread.with the
> Here is what we did (Bob feel free to add/correct):
> Through careful observation we determined that something was wrong
> communications between the terminal and the RS232 port. With theterminal
> plugged in, powered on the computer appeared to stall early in theboot
> process. With the terminal unplugged the computer appeared to gofarther
> (drive would spin, hard drive would light). No characters to thedisplay.
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