I know you say that the switch checks out in test mode. However, you need to check if it is in an "always on state". You can do this with the game off and continuity check on a voltmeter. Really get in there an tug on stuff to confirm it's solid. Additionally, based on your simpletons, you could have:

-two wires or blades touching on the backside of the switch
-a wire fell off and is intermittently making contact with the other blade on start up
-the diode had snapped or a leg has fallen off but is laying across the blade still
-a wire could be soldered to the "always closed" switch lug instead of the "always open lug

Replace switch+diode. Those style switches are notorious for internally failing closed/open. There are moving parts, levers, springs inside a switch that can touch move around in all sorts of ways that they should not. That's a gut feeling but I've had so many of those style switches fail over the years that if it were mine, I would replace it even if it tested good.

Before you order/replace the part though, disconnect the switch wires and confirm that the coil does not fire after 10 power cycles in a row. You can then confirm its the switch.

You need to confirm this by either disconnecting the switch plug at the MPU and powering the game back up or, by disconnecting the wire(s) at the switch. I suspect you have a solder splash on the back side of the MPU, or a bad IC. But at this point, you should rule out the PF, the MPU, or wiring.

Anything is possible but it is much more likely an issue with the switch circuitry on the MPU and not the sol./transistor circuitry. Personally, I would just leave it unless you want to start diagnosing an idividual MPU switch issue.

If it's unplayable then you have not provided the complete picture of the problem. I thought it only pulsed on power up two times and then enters attract mode and plays normally. Can you elaborate more? Elaboration could help eliminate certain causes, saving time resolving this issue.

If this is still true, the problem is likely somewhere on the play field. If switch circuitry were shorted on the MPU, the sol. would still fire after you unplugged that molex header. If it does not, and the problem only presents itself with that connector plugged in, then you are looking for a problem on the PF. So, if the game were in front of me, I would disconnect the switch wires on the outhole and with everything plugged in, observe again.

Can you first go in to switch test and see if any switches are "stuck" closed. If so, unplug the switch molex and retest. This would provide some more useful information to troubleshoot. With all the balls out, you don't want to see any switches active during switch test. You don't have to slip the wire out, just unplug the IJ11 connector at the MPU.

The above means the MPU is probably ok. Otherwise, the coil would continue to fire, even with the molex plug off.

Think of it this way. The PF is an input device or the "keyboard" in the pinball system. If you have a stuck "P" key on your computer keyboard and you unplug the keyboard, the constant "P" letter symptom stops. If you unplug the keyboard and you still see a "P" being typed, the problem is not with the keyboard.

Sorry, I had to re-read everything a few more times. If the PIA (or anything after it in that stream) controlling the game's switches were bad, the coil would continue to fire even after he unplugged IJ11. (As long as that's the only plug disconnected for that test.)

Sw 28 stuck closed... desolder the two wires and put the game in switch test mode. See if the wires are on the wrong lugs, etc.

Just to clarify, you are testing for closed switches, not open switches.

I understand your frustration but just desolder the wires and hold them in place on the different lugs until it works properly. Then solder them back in place. It's all low voltage and will not harm anything if you do this while in switch test. Just keep the wires away from everything else. If you can't get it to work, maybe the switch is defective. Yes, that happens all the time. You could always go to a leaf blade style switch too.

Don't exit switch test until it's working and be done with it. Do you maintain all of your other games?

If you can play through as few games with no issues, I would call it done.

Sounds really inconsistent to me. Can you get the coil to fire like this with IJ8 or IJ10 removed at the MPU? It should never fire with either of those removed. If it does, you have board problems.

Report yes or no.

With those connectors back in place, go in to switch test and test every switch in the matrix for the rows and column in which you are seeing this problem. (GRN-YEL and WH-YEL wires) (Especially right coin switch in the coin door, the C and D stand ups, the out hole, the right drop target, and lane change)

Do ALL SWITCHES ONLY report one CORRECT switch being triggered? While you are checking each one carefully, also check the blades and connections at the lugs of EACH switch. Blades could be touching OR, more likely, a wire could be "floating" inside a lug, making some crazy things happen. Make certain each wire is firmly soldered in place.

Report yes or no.

If every switch works properly after this test, you are going to be looking for something wired wrong, or touching where it shouldn't be, or a bad diode.
It's difficult to track problems like that down, especially if it's an inconsistent problem.

Sometimes, the only way to find things like that are to clip one diode leg, test the diode and switch, then re-solder the clip. Before that though, you can check for shorted diodes or switches with your meter's continuity test.

Given the history, my wild guess is that your coin door wiring could be messed up since the switch in question shares a wire with a coin switch. (SWITCH 28 and SWITCH 4)

-Try unplugging the small coin door plug, just inside the harness along the left side of the lower cabinet and see if the problem goes away.

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Unfortunately, yes.

Working backwards from IJ11--> Q47 --> q43 -predriver-> U5 (7408) --> U46 (LS374) --> U14 PIA -end-

I feel like the outhole was probably ok all along but you initially wired the new switch incorrectly. Now that it's wired ok, the initial intermittent problem (with the MPU firing the outhole coil on it's own) persists. The odd problem is that it's only a problem as the game boots. I hate to suggest shotgunning the board. Can you yank the MPU out and visually inspect the traces around the components I've listed above on the top and bottom looking for bridged solder pads or perhaps corrosion/burnt traces/previously worked on traces?

My gut feeling is that the PIA is firing the coil on boot and that PIA needs to be replaced. However, that's just a guess. You could observe this with a handheld logic probe but if you've not traced/done it before, it may be quicker/easier to call in the cavalry and send the MPU out for repair.

Pin 33 of PIA U14 goes to --> [pin 18 of U46->pin 19 of U46]--->[pin1 of U57->pin 3 of U57]--->Q43(emitter leg)-->Q47(emitter leg)-->pin 1 of IJ11--> Grounding wire to the outhole solenoid

Your specific symptom does not really allow for the transistors Q43 or Q47 to be at fault because they are only "completing the ground" in this circuit. Since that is happening properly, you need to look closer and closer toward the PIA until you find the problem. With a probe, you should be able to see the signal pulse at each of the steps above, when the coil is firing incorrectly at the boot of the game.

I know that doesn't really tell you WHY it's happening but if you want to follow the signal, that is what you should see.

The signal on pin33 of the PIA should only fire the outhole when someone starts a game, and the ball is fed to the shooter lane.

If pin33 is pulsing when you see the coil repeatedly fire when it should not, socket and replace the PIA @ U14. Replacing a 40 pin IC with a socket is no easy task, especially if you've never done it.

You mean the ones above the switch matrix plugs, correct? Those are easy enough to test. Very good insight.

I really hadn't considered that it still could be a switch issue since the game does not fire the outhole SOL during game play, only when booted.