Meaning? Is the problem possibly caused by one of the boards I'm waiting for? Such as the SDB?

Me? A Schematic? Best I can do at this point is verify the wires are all connected and test the diodes. So far the diodes have checked out on the problem parts I mentioned. I'll try to check all the ones I can see.

Thanks for those. I do have hard copies too. My electronic abilities are minimal. I've done more diagnostics on this machine than ever before. Learned a lot already. I've checked every diode I can see and they all check out. The wire braid has continuity all the way through on both sides.

The kickouts and drop targets were working until I replaced the MPU a few days ago.

UNBELIEVEABLE!!! I put the old MPU board in, minus the corroded battery. The machine works perfectly!! I'll contact Marco Spec tomorrow. Looks like I spent a lot of money for nothing. The kickouts, drop targets, and even the pop bumpers work better. They actually bump the ball instead of just giving points. Thought I needed to fix those too.

Since the old MPU had the corrosion I figured it was needed. I'm running it without the battery. I'll swap them out once I figure out the problem with the new board. For now I'm a Happy Camper thanks to all the help from everybody on here.

I have a connector rebuild kit and Molex crimper coming. I'll try the new board again after I rebuild the connectors. This machine is a blast to play. I didn't realize it could be so fast. I love it! I won't be able to set the high scores or other bookkeeping data until I can use the new board.

Update: I called Dave at Alltec. Problem solved. I installed the new board with the screw in the upper rt corner like the old board. This was incorrect. In the new board, the screw goes in the lower left corner. The way I had it was shorting out the board. My mistake, corrected by Dave. The new Utimate MPU works like a champ. Displays and lights appear to be brighter too. Lesson learned. Pay close attention to installation instructions in the manual. Thanks again to everybody.

Although it turned out to be unnecessary to replace all the boards, I now have all four of them to upgrade. The only remaining issues are a few lights not working which is not the bulbs. I need to replace some light sockets. Occasionally something sticks and points continue to rack up when it shouldn't. I need to track down where from. I suspect it's one of my drop targets. Anyway, enjoying the game.