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.

Sort of correct. The game starts up, is essentially in attract mode and displaying credits on credit display, but all zeros on the displays.

The 40-pin interconnect has been replaced, and I verified that the reset circuit is working properly with an oscilloscope.

In fact, regardless of whether the board is in the game or on the bench, if I do a forced reset by grounding the reset pin of the CPU, the board returns to the state where there's a 20 Hz pulse on Q16 and 0s on all displays until one of the controlled solenoid switches gets triggered.

Triggering a solenoid doesn't start a game, but it puts the game into normal attract mode where I can I actually start a game.

Yes. Burned new eprom, installed an Nvram and did a factory reset. Also made sure that I had the correct image for U17 since its different from other games of this series that use white ROMs.

Yes. Burned new eprom, installed an Nvram and did a factory reset. Also made sure that I had the correct image for U17 since its different from other games of this series that use white ROMs.

You are correct. I have a bad habit of using U and IC interchangeably. Bally and Gottlieb schematics tend to use the U designation for ICs.

In case this ever comes up again for someone else, all this weirdness was caused by a bad row seven receive buffer in the 4049 @ IC16. It was shorted to ground. Not sure why triggering one of the controlled solenoids knocked the game out of that undefined mode and into attract mode, though. Replacing IC16 solved the problem, though.