Midway Extra Bases odd board issues - Midway Card cage system (Gorf, WoW, Space Zap, etc)

RobotWorkshop

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I have a Midway Extra Bases that has been running ok. It was definitely overdue for a Power Supply rebuild and a re-cap on the monitor. While waiting on the capacitor kits I decided to pull the card cage to wash those boards and go through them. Plan on adding the clip on heat sinks on the customs to help keep those cool. After washing the boards I noticed several odd things.

- On the custom U15 pin 23 wasn't in the socket. Since the game it running either that pin doesn't matter if it was plugged in. Or it was left out on purpose. Anyone familiar with this? Going to look at the schematics to see if it may help explain what is going on. It looks like a mistake so was going to get it back in the socket after installing a heat sink.

- On the game board U17 is empty. Schematics show it should have a 2114 chip. Since the game was working I assume it wasn't used or needed. Not sure if it should have one or not. Hopefully someone else with an Extra bases can check to see if U17 is populated or empty like mine.

- One of the RAM boards is missing U21 (74LS14) and U22 (74F08) and instead has jumpers on the pads on the back. Haven't read any notes that this was needed for Extra bases. Has anyone seen this mod before? Again, someone with an Extra bases may be able to confirm. But I think only the cocktail had two RAM cards and that the upright only had one.

So I've found several things that don't look right which was surprising since the game seemed to play fine. I'd like to find out and confirm what is correct so I'll be able to finish the game once the other parts arrive.

Thanks in advance for any input.
 

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