Battery retention voltage will only cause you to come up in diag mode, not cycle through it.
If you disconnected all you do have a logic issue. If memory serves, and this is a big if, your probably looking at a 7404 that is the chip used to decode the coin door switches. But your best bet get the boards to a good repair guy who will fix it, replace all the SCANBE sockets (if it has them) and replace the 40 pin interconnects.