Working on a Williams World Cup. When the game is turned on, the displays are lit up with all 0s, and there's a ton of flicker, and loud buzzing. The coin lockout relay pulses in time with the buzzing. The game is completely unresponsive to coin switches, start button, etc. Triggering any of the switches for controlled solenoids, however, triggers that solenoid to fire which immediately stops the flickering, stops the buzzing, stops the coin lockout coil pulsing, and puts the game into playable mode.
Removing the MPU & Driver board from the game and powering it on the bench and monitoring the inputs/outputs with oscilloscope & logic analyzer, it behaves identically. On power up, a 20Hz (low) pulse appears at the base of Q16 being generated by the PIA IC5 pin 17. Blanking signal is High. Everything stays in this state until I trigger one of the switch inputs corresponding to a controlled solenoid which fires that controlled solenoid and sets the game into a usable state.
I've replaced IC5, and tried burning new EPRoms because the old ones were crumbling. I got a U17 that is supposed to be correct for World Cup since it was different from other games, but this behavior makes me wonder if it is correct or not.