I get a call for this William’s Diner that has coils and flash lamps locking on. The first problem was the sub playfield shooter was locking on. The coil was melted so I replaced it. The associated TIP-36C was blown as well. After replacement, the coil would still lock on.

The Auxiliary power driver board had a bunch of hack repairs and the A/C relay wasn’t working. I ordered a new one and returned to install it a week later.

I put the new board in and the game plays great for 2 games. Then I let it sit for a while then the sub playfield coil locks on and blows the f@&king TIP36C again! The coil wasn’t damaged but I disconnected it anyway and turn the game back on. Then the Buck flash lamp locks on. I take the bulb out and another one locks on.

The guy has a Whirlwind that uses the same aux power driver board so I swapped the new one in to verify it was good after replacing the TIP36C again. The board tests fine. I can’t do any more in this guys basement so I pull the logic board and test it on my bench.

I put in my test ROM which pulses all the outputs on the PIA’s from low to high and everything checks out until I notice a few outputs locking on. Connector 1J11 pins 6-9 particularly.

One thing to note is that those outputs aren’t driven through PIA U10, they are driven directly off the data bus through U28, a 74LS374. That wasn’t the problem though. The ‘374 feeds a 74LS08 which is part of the blanking circuit.

If you missed my Data East Teenage Mutant Ninja Turtles article covering what that does, you can check it out here.

I noticed as I flexed the board, the problem would come and go. One thing to note is that the logic board only had two screws holding it in the game. That’s why the game would intermittently play fine.

U19 had been previously replaced so I didn’t think it was the problem. I threw it in my tester to make sure. The problem was the previous tech put a shit socket in and when the chip doesn’t get good contact, coils and lamps will lock on. I tossed the socket and just soldered the chip directly to the board.

Sockets can be a convenience, but also a weak point. Make sure you use a high quality dual wipe socket for your chips. Anything less will cause more headaches down the road.

I returned one last time to install the board and verify my repairs. I also brought a set of 8 screws to secure the board in the game. Diner is playing great again.

You can see in the pics below the schematic diagrams of the relationship of the coils/flash lamps that were locking on.

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During this call I also had in intermittent switch problem on his William’s Indiana Jones, that article will be coming soon……

Till next time, Frank