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.
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.