Tron progress halted (damn)

I will check the version when I see the game later today.

  As for what I was seeing yesterday when working on the boards, not
sure if can explain what was going on but I'll give it a shot. Going
off of Brad's advice, I was investigating the LS138 decoder at E6 and
its interaction with the memory chips.
  Using a probe I found that both the enables on D6 (2764, pins 20 & 22)
were high, thus explaining why the memory was not enabled. Tracing this
back to the LS138 gave me results of good Vcc and GND, as well as clock
activity on both enables E1 & E3 (E2 tied to GND) and the addressing
inputs (A0, A1, A2) to the decoder. On the output sides of things,
there seemed to be an issue, as some of the lines seemed to be stuck
high, including Select 4 (D6). Again, this seemed like a clear reason
why D6 was not being accessed. At first I thought this was a good
indication that the LS138 had indeed managed to give up the ghost.
  However, wanting to confirm exactly which addresses were or weren't
being selected, and having access to one, I hooked up a logic analyzer
in a further attempt to determine exactly what was going into the LS138
on the input side. If for some reason there was never a command to
address D6, then of course it would never be enabled. When trying to
acquire the bus activity the next time around, I found that I had
stopped getting activity off the bus into the inputs of the LS138. So
now I had nothing to trace...with no activity in, there was of course no
activity out. Power cycle, nor board resets seemed to correct this
situation. On a reset, there would be a brief (2-3 sec) period of
activity, then all would go flat again.

  So now I am again at a loss concerning where I should be looking. Do
I continue to suspect the LS138, or do I maybe have a culprit further up
the chain? Does this sound like a failure in an IC, or a power
problem? Some other common beginner's error? As near as I can tell, I
have good power and no Reset issue.

As always, thanks for reading, and thanks for everyone's help so far,
and in the future.

peter jones wrote:
> i can sort the rom images,
>
> there are 4 versions, you need to tell me what it says on the rom stickers.
> http://www.arcadecollecting.com/hacks/tron/
> may also be of interest.

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Received on Wed Oct 31 12:41:47 2007