MPU and Opto board won't do anything here.

Look at the 8-Driver board, connected to the MPU in the backbox with the 'DISPLAY' (medium) ribbon cable.

So if you enter Click Test, take the front panel off the clock and stick a piece of paper in an opto, it's never reported as being blocked (closed)?

And you replaced the 8-driver board in the backbox, no change, AND you replaced the MPU, no change? And the clock works in another game?

Test the optos. It's the only thing left, despite working in another game. Are the optos OPEN or BLOCKED (in test mode, are there 'X's in the squares, or not) normally in the game?

If what you say above is all true (not saying you're lying, just spelling it out) then it's a wiring issue in your game - your'e going to WISH that it was a board problem.

Depending on whether the optos are reporting open or blocked, it's likely a voltage problem - bad plug, broken wire delivering GND to +12 to the clock boards.

The wires in the cable going to the clock are probably broken inside the shielding. Right before the connectors that goes to the clock board

A buddy of mine bought a new clock board only for the new one to not work either.

I checked the wires for him and sure enough they looked fine but were broken (open circuit) inside.
More than likely right in the drastic bend they have going through the plastic clock housing. Right at the molex connector.
Thats were his were.
His had a few broken wires on each plug
But visually they looked fine. And well connected.

Anyone else have a similar issue? Did you ever determine the problem?