I will concentrate on Williams Sys 6 / 6a MPU boards - those are usual in a FirePower Pinball Machine.
You *can* run Firepower Games from System 3,4 and even System 7 CPU boards!

Making a System 3-4 MPU run Firepower is more like a video game hack, and I don't recommend it to the faint hearted:
Leon's System 3-4 method But it does work and is credited (certainly by me) to Leon Borre of the Williams Test ROMs renown.

Sadly, I heard a few years ago that Leon passed away, but the documentation of his work is still at his excellent site - not pretty to look at but well worth a look as the technical depth is there. The site was once called www.flipper-pinball-fan.be but the domain seems to have been taken over now. RIP my friend, I couldn't have learned how to fix Williams MPU boards without your Test ROM, knowledge and willingness to help.

I actually run my Firepower on a System 7 board, which has the jumpers and addressing to support an easy downward compatibility.

I needed the extra Game ROM space for modified ROMs running 7 digit scoring (saves high scores up to 10,000) and has some other nice game enhancements.

Details of running System 6 games on a System 7 MPU, including a new jumper method I devised. Some of the linked page is still under revision, so apologies for broken links. Others may have decided to remove access to the info on their sites.

Enjoy! Especially if you own a Black Knight pinball as well. Another fantastic Steve Ritchie game released in 1980, the same year as Firepower.

So many pinball breakthroughs were made in a short space of time in the early 80's.

Williams Sys 6 / 6A boards Blanking Signal:

At the risk of getting involved in the "blanking signal" saga, I offer the following information from my experience:

1.Blanking can really only be checked once your board is running properly with game ROMs installed, and with a Driver board connected.  You need to check blanking can go high properly (at TP4) before moving a board from the "test bench" to a working machine!

2. With blanking low, the game's lamps, displays and solenoids shouldn't be able to be turned on. This is because the lamps and displays could be damaged if they were not being "strobed" by the running program.

3. Leon's test chip "pulses" the blanking signal - but doesn't test that it works properly as a watchdog timer.
I had a board that would boot with Leon's test chip installed and even strobe the blanking circuit, all memory tests passed - yet if placed in a game with game ROMs it would fire ALL the solenoids at once and blow the solenoid fuse.

The fault turned out to be the Dual-Timer (556) at IC23 in the "blanking" circuit- which I hadn't tested with game ROMs installed. When I did check TP4 I found out it was low. This chip doesn't fail often, but in any case is cheap and so should be very easy to replace.

If the board boots with the game ROMs installed and it passes the self test (both LEDs flash and then go off), then always check for the Blanking signal at test point TP4 on System 6 and 7 boards. On System 3 and 4 boards and also as an extra check on sys 6/7 boards use pin 37 of the 40-way interconnect with a good Driver Board connected. It should be around +4 to +5 volts, if you don't get that working - don't install that board set in a game!

What to check WITH GAME ROMS installed (you will need to connect a working Driver board):

0. The board boots with the game ROMs installed, it can pass the self test (both LEDs flash and then go off).

1. If you have a logic probe, you can check pin 8 of the 556 timer IC23 (Top left chip near TP1) for pulses. You need a transition from to high and then low again less than every second. If no pulses, then the 556 watchdog timer times out and blanking stays low.

2. The pulses are driven from port PA2 (pin 4 ) on PIA IC18 which is being pulsed every .8 msec. If this is not pulsing, then perhaps the PIA is bad, CPU is bad (you changed that Scanbe socket, didn't you?) / or the program is not running for some other reason. Also as a last resort, suspect PIAs on the attached driver board.

3. From Mark's guide on troubleshooting, this nugget may also help:

Try looking at the outputs of IC25 (a 4020 1ms Timer). If the interrupt signal is not being generated at the correct speed, then IC18 will not generate the required "pulse".

A likely cause for a blanking signal failure is a timer chip failure (IC23 was the fault in my case) a bad capacitor at C31, or the transistor Q5 a 2N4403 (which you can test quickly with a DMM on the "diode setting").

In System 3 and 4 boards, the 556 is also used to generate the IRQ signal, so suspect C31 or Q5 first. On System 6 boards the 556 is only used for blanking as is the 555 on System 7 boards.