Disconnect the playfield before turning the game on.

Post pick of mpu, my firepower was not very reliable till bulletproofing it, reflowing all tbe pins on the conectors and replacing the 40 pin interconnect, also bulletproofing the power supply. Search for vid1900 bulletproofing guides on here.

Looking at your pics your blades on the leaf switches have broken. Those need to be replaced but don't think that would make the mpu do funky stuff. Post a couple pics of mpu and maybe someone will see something you're not.
-Mike

If you want a reliable System 6 board set, you really need to do the following:

1) Reflow solder or better yet replace all header pins on all connectors (this includes the sound and power supply boards)
2) Replace all the ROM, CPU and other sockets that may be on the boards
3) Clean the pins on the CPU and ROMs
4) Replace the 40 pin interconnect (both sides)

There are some other enhancements you can perform but those are optional and don't effect the reliable operation of the machine.

If this seems like too much work or too much money to spend on your original boards, sell them to me and buy a new one.

#1 - Replace both sides of the 40-pin interconnect first.
otherwise you are just farting in the wind.

The game will not start with the playfield disconnected. It needs to see all 3 balls to start. The displays turning off may be normal, not sure about that one.

Rottendogs work well on firepower but are having problems on system 7 games.

Someone mentioned this earlier but it’s worth repeating. In addition to the mpu/sockets/connector work, bulletproof that power supply. Replace those caps, particulalry the giant one that filters that 5v line. When that one cap starts to flake you get boot and reset issues. Even with a new rottendog mpu if that 5v is failing you aren’t getting anywhere.

Understood that you're not looking forward to doing a bunch of board repair and may just replace with new, just be sure don't chuck those original boards. Remove the batteries and store the boards in a safe place. Getting tougher to find good repairable examples.

Richard