Have a spare MPU board for a WPC95 Congo. Tested this by swapping in a known good eprom, known good G10 security chip (for Congo) and a known good 6809 CPU. The board will boot into factory settings restored, then after hitting any of the coin door buttons the game will first show the testing and rom revision screen and the serial number along the bottom will be all zeros, then it just shows "G10 Error" on the screen and you can't do anything else.

Is there another specific chip or area that I should be looking at on the CPU? Anybody seen this before.

Looks like and U14 and U24 (74HC374) connect directly to this

U23 (74HC237) adn U13 (74ls240) both look to be connected to the outputs on it.

definitely 574. I pulled the old ones and didn't realize they were not 374's until I went to replace them and realized i didn't have any 574's. I'll update when I get some in.

replacing U14 and U24 got the board to recognize the G10 chip, but I still had a switch matrix problem. You could see random switches activating super rapidly. Either turned out to be U15, U13 or U5, not sure which one did it but after replacing all 3 of those the board is completely working.