Re: Space Duel Tech

On Fri, 18 Sep 2009 23:35:04 -0700 (PDT), you wrote:

>Out of ideas, so I thought I'd ask about on this one.  Space Duel board was working and then got a jolt from a failing ARII.  Initally had one high tone, so I replace the first RAM, and was rewarded with two high tones.  Replace the second RAM and the game played blind...for about 2 minutes after which it gave me two short low tones, and two long high tones.  At this point, I replaced the AVG chip, processor and Pokeys with no change.  Stationary vectors on the screen, solid coin switches. 
> 
>The manual is no help with this tone combination.  I haven't switchd out the ROMs yet as I don't have a reader to check them.   Anyone have any ideas?  I do have a logic probe if anyone has anything specific for me to test.   -Malcolm

        While I can't think of anything specific off the top of my head, I
would say this: don't get so focused on the "major" chips (CPU, Pokeys,
etc.) that you overlook the "little guys"; i.e. the 74LS-series logic chips
that glue all the big guys together. 74LS-series TTL chips, at least in my
experience, are *notoriously* intolerant of overvoltage conditions; that
failing AR-II may well have whacked one or more of them, in which case the
major chips may be working just fine, but not be able to communicate with
each other because some 74LSxx chip in between them isn't doing its job any
more.

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solarfox@removethis.triluminary.net (Gary Akins jr.)
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Received on Sat Sep 19 09:47:16 2009