It's an eight-chip set on a SUB2 board, using the gundogs PCM ROM. The MAME version was a six-chip set using Raiden_F PCM.
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In other weird things, I couldn't get trap's SPI Revive to create usable ROMs so I changed the region code on Jet, from JP to KR, so I could play it on the new mainboard. Turns out this introduces a few bugs. Right from the name entry screen before the game even starts, the sounds loop, garbage fills the screen, and there's gibberish English text snatched from all parts of the game. Since I hadn't heard that changing the region code did anything but change the region, I thought this might be something other people might be interested in.
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And the Korean mainboard I picked up seems to be a cost reduction unit. It has a stereo select jumper, but the 4-pin stereo header was not installed. Neither was the ten-pin header near it, or the extra connector near the JAMMA power, the cubic component near there, and it was missing the P3 and P4 connectors and associated filters. Never seen one like this before. Doesn't look like they were removed, seems like they were never installed.
Not sure if anyone cares, or if this is a version no one's seen before, or what.
Pics:
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Finally, because board flex is an SPI killer, I made a few fixes for it. First, my Raiden Fighters didn't come with a cart cover, so I made one, and built some central supports in so the cart wouldn't flex when installed. I also created a bottom cover for it. I liked them so much I removed the original covers for Viper and Jet and made covers for those too.
The main PCB has a central support that locks the board to the substrate it's mounted on, preventing flex when carts are added or removed. You can download the STL files and print your own if you like.
Pics:
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