Re: battlezone

On Fri, 17 Dec 2004 12:39:35 -0500, you wrote:

>in test mode i get a variation of a square wave on all the address lines
>but in normal mode 4 address lines don't look right. i hate to keep coming
>back to the address lines, but 3 of the lines go to the decoder and the
>output from the decoders don't change. it seems the thing to do is change
>the decoder chips, but the 3 lines feed 4 chips. i just don't see all the
>chips going bad at the same time.

        "An ancestor of mine once maintained that when one eliminates the
impossible, whatever remains, however improbable, must be the truth."
(--Spock, from STAR TREK VI)

        While all four going bad at once is unlikely, it CAN happen. Some
chips CAN be more prone to failure than others, for all kinds of strange
reasons. (Internal complexity, variation in design from one manufacturer
to another, the kinds of signals they're expected to deal with, phases of
the moon, local variations in the neutrino density of the space/time
continuum, etc. :) ) Even within a particular logic family or
manufacturer, some chips are less tolerant to supply-voltage variations
than others, for example, and will more readily commit seppuku the first
time the +5V rail creeps above that +5.25Vdc "max Vcc rating."

        Are all of the decoder chips the original ones, and are they all of the
from the same manufacturer and of the same date/batch code? Or have one or
more of them already been replaced before? (If they're all originals from
the same manufacturer and batch, there's always the outside chance there
was a minor flaw in that particular production run.)

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http://lonestar.texas.net/~solarfox
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Received on Fri Dec 17 13:27:43 2004