Firepower is having an issue where it will "phantom" close the previous switch that was activated after another switch is closed. This is matrix wide and not limited to one row or column.

Method of test:

Game is in switch test mode. Close a switch (any switch). Display shows appropriate switch activation. Close another switch. Ditto. Single switch closures show no issue.

Problem:
Close one switch multiple times, say 3 to 5 times. Display shows appropriate switch activation. Now close another. Display shows new switch activation. Wait about one or two seconds. Display shows previous switch activation.

Basically the problem is that there's no issues when the same switch is closed once or twice in a row but in a area of the playfield where it would be closed many times in a row and then a new switch is closed the game "thinks" the previous switch is still activated.

Once again, this is game wide and not limited to a particular row or column. Also of note, this also occurs with solenoid activated switches like the flippers but it does not fire the solenoid though. For example, in switch test I can press the right flipper, switch 45, several times. It shows 45 on the display. I then press a coin mech switch, say #6. The display shows 6 for one or two seconds and then shows 45 again but the coil does not fire for the flipper, which, I guess, is a good thing.

As of right now my guess is the switch PIA (6820) at IC 11 but would appreciate any input you have before installing a new one (actually 6821). Thanks.

40 Pin connector has been replaced as well as all header pins desoldered and re-soldered.

Yes. Manually activating a switch using an alligator clip on the driver board yields the same result. Example, activate switch 7, displays "7", then move to 6, displays "6" for a second then shows "7" again.

New switch matrix PIA installed and socketed. Unfortunately, no change. It doesn't matter which way I test the pins whether with starting with 2J3 or 2J2 it still does the same thing. Touch one pin once and then another, all is ok. But if you tap one a couple times and then another it will display the correct switch number and then go back to the previous one.

Alright guys. For right now I'm gonna have to attribute this to "ghost in the machine." Even though it doesn't operate properly in switch test, I have no issues with incorrect switches closing during gameplay. My girlfriend and I played about 20 games on Firepower with no unusual behavior. I even manually closed the same switch several times and then another just once to see if it would register the previous switch hit which it did not. This was how I noticed the problem to begin with. One of the three score switches off to the left of the spinner would constantly register and score. It no longer does this.

Any other thoughts would be appreciated but for right now it's playing properly. Thanks to all that responded.

System 6. Sheesh! What a PITA. I want another WPC.

Thanks guys. Any further issues and I'll just replace all four of those switch chips. It's just that I had an extra PIA on hand and since it was game wide i figured that might be the issue. Of note all my sockets are RN's, which I've pulled all the chips, cleaned, reinstalled and checked every pin for continuity. The exceptions are the one's I've replaced which include the switch PIA and the sound board PIA which caused an earlier issue. I used the machined pinned strips which I like.

I don't have the test ROM or a logic probe but I don't have a problem logically shotgunning a board repair. As long as the parts are cheap. I'm pretty decent with a soldering iron and I managed to not damage any of the plated through holes on the 40 pin switch PIA. Hurray for me. :p

Oh and don't worry about the schematics. I got a crusty original schematic book for Firepower.