One of the first things to do to that small driver board is to find the ground on it and solder a big fat wire to that and tie it to the backplane ground. The factory wired ground to that board goes over to the far left side of the main driver board and is 1 or 2 wires on an IDC connnector there. It that ground connection there gets loose it will wreak havoc on the ball shooter coil transistor and possibly the auger motor. On my first hyperball (i think I've had around 7 by now) that ground was loose so that caused the fire signal from the MPU board to float and this made me burn up around 4 or 5 of the shooter coil transistors ($10-$15 each) before I located the problem.

Those 2 devices get their CPU signal from the two small transistors (2N3904?? I forget exactly which) on the middle right side of the main driver board. Start there to see if the signal is making it from that driver board over the the small driver board.

That was a fair price. The route operator I worked for threw all of them into the dumpster when they were less than a year old. They went from earning hundreds of bucks a week to essentially zero in only a few short months. Distributors tried to close them out but no one would even buy them. Distributors would not buy them back. They said toss them in the shit can which we did. Kept the display board and IIRC, the power regulator board. Maybe a couple complete board sets that we later tossed. I kept one backglass but everything else was smashed up and tossed.

Williams had the audacity to change the sign in front of the plant to say "Get Hyper" and "We're the talk of the Industry" at that time.

You lucky muh! Everything MrBally said is probably right, since a robust working Hyperball is rare as hens teeth... but man, I've always loved this weird machine.