Game is Flintstones

It started odd behavior where it would register as if the Coin Door was open randomly through the game. It would go long periods without, then it would start doing it on and off frequently. At the time, I thought it was a dedicated switch like the coin door buttons, but with more time and bigger screen, I see it is in fact in the switch matrix as col2-row2 in Flintstones. The diode for the switch looks to be on the coindoor interface board.

At first, I jumper'd the switch's pins at the coindoor interface J9 hoping I could bypass the switch and keep the game going on route. But even when jumper'd, the game was doing the 'Coin Door Open' message intermitently.. on and off, almost independent of any game input. Shouldn't this be a Normally Open switch? If N.O., and jumper'd, I would expect this to negate any diode/short issues.. as the problem is the switch is registering open, instead of false closed.

So this leads me to possible wire breaks between the coindoor board and the MPU, MPU J212 issues or maybe row/driver chip issues. But as far as I can tell.. I'm not seeing any other switches flaking on that row and column. Since the coindoor has it's own connector on the MPU.. maybe this means it's a physical issue at J212.

The game is WPC-S so it has the stand-off battery holder.. and I don't see any obvious corrosion issues, but I've also not had the MPU out of the game.

Any other tips or guidance?

Also, this schematic from the manual has to be wrong right? Why would a switch column and row be direct connected as highlighted by the red line here? Col 2 to Row 4 on the coindoor board

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I had did that.

I tested the switch itself with multimeter (registered fine) and jumped output pins on coin interface board and switch state was still fluttering.

Thats why i was already looking upstream and needing to know if switch was no or nc

Eta- obviously from my multimeter test its no (duh). So its gotta be a break in the path. I gotta see if any other switch is also affected i guess to isolate if row or col

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Started by just trying to jumper the row/col and found this…

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Wasn’t easy to see until I removed the connector because of the wpc-s battery holder and the fact only this connector and the battery holder had any crunch on it. They obviously cleaned up the battery holder before but never the connector under it :/

Back to the bench it goes…

Yeah, it seems to be a vapor effect (up) and a drip effect down. Then of course once on the board, a creeping effect across tinned connections. The transistor tabs on the light board on bally's love to get crud on them from the MPU battery.

I wish I had a picture of before I pulled the connector - there really was no visible sign on the connector.. it was all behind the tab. There was some hints of crude in the battery holder, but nothing looked recent and the board looked clean. It's always hiding Like a used car.. good enough to drive off the lot.. breaks in a week.

Also first time I had really seen so much BLUE in the corrosion. Must have been smurf powered batteries

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ETA: now zoomed in that photo does show a bit more corrosion on some of those resistor and cap rows... but I think it looks way worse in the photo then live. It barely looks dull live.. but obviously there is some crud exposure there too

So replaced the header… replaced the connector… and worked.. for like 30 seconds.

It was so weird… would look right with sw24 on… would push in mem protect switch (22)… and sw24 would go off! Hold sw24 in and it would start flickering.. and eventually both switches would just settle as off after switching on and off a few times. So wth.. even the coin door switches started freaking out. Now I ultra confused.

Tested the row to col pins at the mpu and everything was fine. But full system kept failing. I tested col1 and those switches were stable. But col2 switches… flaky.

After pulling the col2 connector pin and checking the crimp and testing again…. I thought maybe the diode was starting to fail open? So i goto pull the coin interface board…

And look at what is behind our locking tab…
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And the pins…
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Wth… somehow only 2 of the pins have crud… while nothing else around does. what’s pin2 there?? Yeah… col2 pin.

Freaking hidden crud wasted over an hour of my time chasing ghosts. Again neither side, crud was visible when the connector was attached. So always pull them and check before giving them any free passes

Was done when the mpu was out for the switch header… as well as replacing the 5/12v header and connector

This one was interesting in that the crud was pretty well hidden. The joys of ‘discovery’ when maintaining games people bring you