Long shot but hoping

I have a Midway grid board which is in constant reboots after it passes
self-test.

This uses the Athens board.

Crusin' Exotica is also on the Athens board.

I picked up an Exotica which is working fine.

I did a rom swap Grid -> Crusin and get a mess of rom checksum errors.

Digging around a touch I realized that they use an Altera Max EMP7128S at
U29 as an address decoder. The Crusin boards appear to have a different
memory map than the grid. I was able to rearrange some roms and combine
four into two to get all but two roms to pass test. But it looks like there
is no way to get the other two roms to come through.

The Mame sources for this board imply that is should work but I was probing
the chip select line (pin 11) at each of the sockets when the board did it's
checksum on the problem roms. One socket triggers for just a moment and
then the board fails the rom.

The board has a 10 pin connector right next to the Altera chip, I am sure
it's a jtag port. The Grid board has a hand written "AB" notation on the
part id label which makes me believe they just flashed the board before they
installed the roms.

Problem is I have 0 experience with Altera parts and I don't have a clue how
to try getting the code out (which could very well be protected). I am
wondering if anyone here has any ideas on how to pull the code out on Grid
and then reprogram the Exotica board. My only other alternative is to
remove the chip from the exotica board and then pull the one from the grid
and put onto the exotica. Doable if I am lucky. That's a really fine pitch
100 pin part.

I tried arcade-service.com who say they work on these but they have been
just shy of useless.

David

PS, oddly enough the crusin chips pass self-test on the grid board. I
suspect they loaded both memory maps into the chip and then just select the
correct one on boot using some configuration register. But as the grid
didn't exist when they did the crusin boards..

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Received on Wed Apr 10 00:44:57 2013