Quoted from PinballManiac40:
Too much involved to get working properly to work in all the different games. I am sure the design could not have been tested in every possible game.
This shouldn't have been an issue. The system 11 games don't have anything out of the ordinary to keep multi-game platform from working. Just not paying attention to the very minor differences in the 11/A/B/C/DE variants. (the major hurdle being the sound system on the 11/11A/11B, so if 11B games work, then they should all work)
Special solenoid inputs/outputs are different between the DE and Williams games. I think he remembered that the outputs were different but maybe he forgot the inputs (11B and 11C don't use the inputs, 11 and 11A do) otherwise 11A and 11B are functionally identical (the unused switch opto circuits on 11 and 11A get deleted on 11B, and the sometimes populated audio amp on 11A's was only used on the first three 11(no letter) games and not needed for the 11A titles.
11 and 11 A difference are almost as simple. 11A has the diodes already installed on the special coils so that's not an issue going backwards. Only real differences are the audio section has an amplifier that is needed on 11 but not on 11A and the 7 segment display instead of 3 diagnostic led's.
The system 11 boards all shipped with 6116 RAM installed and only the first DE had that sized ram. 11B and 11C had extra pads and jumpers to install the 6264 that all the rest of the DE games needed. AFAIK you can run any of the system 11 games with the 6264 RAM.
If you are saying that you can't get the rottendog board to work/boot in your FIRE pinball sounds to me like you have a currently dead board. For a dead board I'd price it at $100-$150. You should be able to get the board to boot and play and the only issues you might have would be the special solenoids and/or sound.