It all started by changing my batteries in my Starship Troopers. There were some older alkaline batteries that had begun to corrode the springs inside the battery tray on the cpu/sound board (520-5136-00 rev D). There is no indication that the corrosion had spread beyond that other than an intermittent connection if the battery tray wasn't secured properly with a zip tie. After putting in the batteries, I had begun to notice some oddities in the game that have gotten progressively worse even as the game isn't being powered nor played.

I turned the game on to play the day after changing the batteries and noticed that the stepper motor that drives the Bug Warrior wasn't completing its travel, getting stuck half way down the 6" path. I proceeded to troubleshoot the stepper motor itself but all seems to be fine with it. Once installed, it doesn't have enough oomph to move the attached Bug Warrior.

ALSO, the bottom of three bumpers is triggering the switch, but not popping. Tests from the on-board testing don't pop the bumper but grounding the transistor does.

THEN, the auto-launcher coil doesn't fire, neither from the on-board test or by directly wiring it as Dr Pinball had me do.

NOT ONLY THAT, the yellow flashers don't work now. All other sets of flashers do.

IN ADDITION, the entire row 10 is out on the lamp matrix (7-segment display on the playfield plus shoot again - all stopped lighting.) On-board testing doesn't light any of them.

FOLLOWING THAT, row #2 on the lamp matrix is out and will not light through on-board testing.

LIKEWISE, most of column #7 on the lamp matrix is out too, but not the whole column. Rows #7-9 light fine.

Things worked fine until I changed the batteries on the cpu/sound board. All LED voltage indicators on the I/O board (520-5137-01) are lit (the 50V turning off properly when the coin door opens). I've reseated all headers' cables on the boards, flipped the ribbon cable that connects the two (red wire on pin1) and done some rudimentary continuity tests from the headers to the failing yellow flash lamps and coils that don't fire which seem to indicate that connectivity is fine.

Indicators point to something bigger going on that I'm missing. I've gone over the wiring diagrams for days and haven't been able to find anything that puts these things into the same realm other than one board or the other failing in a way I can't wrap my head around. I'm by no means an electrical engineer or know anything but the basics of circuits so it's difficult to understand what's going on. (My soldering is in no shape to remove and test components individually.) The game boots, plays fine, stays powered, but many board-controlled objects don't work. All of this seemingly happened within a day or two of changing the batteries.

How do I determine what exactly the failure is here? Where do I go from here? It's a little overwhelming on how fast it's gone downhill. Any help would be great.

Stumped.

First thing I did tonight was to check the battery tray area and it turns out that the two solder points beneath the tray itself aren't solid. The solder-side of the board seems fine, but the voltage just doesn't show 5V correctly during testing. It's way too intermittent to be a solid connection. I'll be removing them. I'll probably wire in at least a remote tray for now and get rid of this tray altogether. I know it's not immune to corrosion using a remote tray, but hopefully between it and the lithium batteries I'm using are enough to warn me well in advance if something does go wrong.

The game is going on 17 years now. Is it worth replacing the IDC connectors on the boards? Do they eventually 'wear out' over time?

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_{Post edited by ExitWound : Added final thought}

I removed the battery tray tonight and sure enough, the negative solder connection had completely separated from not the solder joint, but the tray! The lead was literally in half, only making connection when the tray was secured by a zip tie. No sense at this point going too much further until I can make sure a new tray is used and the connection solid. Once that's done, I'll progress down the line to see what might be failing on its own and not related to this.

I'll be using lithium batteries but I will remotely mount the batteries at noted above. The corrosion WILL travel up the remote wires with time though. Just will take longer for us to notice.

So I installed a remote battery holder today and that seems to be working fine now. There's no voltage craziness when I touch the tray or the wires.

I put everything back into the machine and I had the exact same problems. Same columns and rows out. Same coils not firing. I was messing with Dr. Pinball again, testing the auto-launcher and I could get the coil to fire by grounding the transistor as it told me to. Its solution: "Replace the I/O Board. Replace the CPU Board. Use the switch matrix to test switches." Well, thanks there Dr. Pinball. You're a real help.

BUT upon inspecting the coil on the auto-launcher, I must have wiggled a short. Everything works now. Every single flasher, column, row, and coil that wouldn't fire before works just fine now. I can't for the life of me figure out where the short is or why it would affect so many systems. The ONLY wires I touched were the auto-launcher wires, two of them.

Any ideas?