(Topic ID: 56566)

Firepower - Switch Matrix Issue - Phantom Closures

By dtown

6 years ago

Topic Stats

  • 19 posts
  • 6 Pinsiders participating
  • Latest reply 6 years ago by Purpledrilmonkey
  • Topic is favorited by 3 Pinsiders


Linked Games

#1 6 years ago

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.

#2 6 years ago

Replace the 40 pin connector between the MPU and Driver Board before you proceed with anything else.

I had the same issues and replacing the 40 pin fixed everything. I could actually get all sorts of crap to happen just flexing the driver board near the 40 pin.

#3 6 years ago

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

#4 6 years ago

Pull the switch plugs from the driver board and activate switches by jumpering rows to columns - do issues persist?

#5 6 years ago
Quoted from Purpledrilmonkey:

Replace the 40 pin connector between the MPU and Driver Board before you proceed with anything else.


#6 6 years ago

Put the machine in switch test.

Pull the connectors off driver board 2J2 and 2J3.

Using a jumper wire connect one end to pin 1 of 2J2.

Touch the other end to each pin of 2J3 - note whether or not each touch registers only once.

Then reverse, pin 1 of 2J3 and touch each pin on 2J2.

If the board passes this test, the problem is on the playfield/in the harness.

If not, since it's not limited to a specific row or column I'd consider the PIA as a problem, though it would be best to check with a logic probe and the test ROM.


#7 6 years ago
Quoted from Purpledrilmonkey:

Pull the switch plugs from the driver board and activate switches by connecting rows to columns - do issues persist?

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.

#8 6 years ago

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.

#9 6 years ago

Can you try it in a different game?

Make sure you don't have a switch stuck closed. This can confuse the game.

#10 6 years ago

Could be a combination of faults between IC15-18. Test ROM and logic probe would help. Assumes all previous work is good including 40 pin replacement.


#11 6 years ago

Yes, you replaced the 40 pin?

Yes, you replaced the two 7406 and 14049 before replacing the PIA?

#12 6 years ago

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.

#13 6 years ago

If I had to guess I would say it's a buffer issue in the diagnostics mode. Could even be a function of the way the diagnostic code was written.

In other words, if it works in game mode don't worry about it, probably nothing wrong at all.

#14 6 years ago

I would replace the 7406 and whatever the other IC is (name escapes me) prior to replacing a PIA. You'd have more consistent issues if it's truly the PIA in my mind - a test ROM would be the way to diagnose that. Bad IC's between the PIA and your headers can connect all sorts of crap wrong and constantly. If you have further issues I'd be replacing those (or even just the crappy scanbe sockets if they are socketed - I believe some are?).

#15 6 years ago


To the above poster the other IC is a 4049. The 7406 and 4049 IC are both prone to failure more so than other ICs.

#16 6 years ago
Quoted from barakandl:

To the above poster the other IC is a 4049. The 7406 and 4049 IC are both prone to failure more so than other ICs.

Yep, I'd do those first if I was just shotgunning.

#17 6 years ago
Quoted from barakandl:

To the above poster the other IC is a 4049.

Thanks for providing that. I have the damn things at home - you'd think I could remember. I didnt want to start digging schematics up at work (again )

#18 6 years ago

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.

#19 6 years ago

I dont have a test ROM or logic probe (yet haha) either. I typically just start replacing parts starting at the low level or the easiest parts to check/service, and moving closer to the CPU itself through diodes, transistors, the ICs, the PIA, etc... making sure each part I replace isn't failing again. As long as you have the parts on hand it's easier than trying to source a test ROM in my part of the woods.

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