Hi. I could use some help from switch matrix experts. I've developed a problem on my Bally Special Force. When the Bomb O switch is closed, it triggers that switch and the right bumper switch. I've circled both in the switch matrix diagram below. I've checked the diodes on both switches, and they were good. I replaced them just for good measure, but the problem persists. Am I right it it is likely a short (perhaps a diode) in the column (think row with other games) that contains Bomb B, Bomb O, Bomb M, Bomb B, Capture D.T., and Weapon D.T.?

I just started playing the game again after a bit of a break. I was waiting for a new solenoid expander relay board which I replaced. I did not go anywhere near those switches. However, it is possible that just the process of lifting the playfield knocked something together.

Thanks in advance for the help! (I'm not great with switch matrix issues.)

Switch Matrix annotated (resized).jpg

Thanks for your replies.

I checked all the switches in the row and the column, and there were no obvious shorts. I'm not sure how a capacitor would cause this problem. I've had capacitor issues before, and they seem to behave differently.

Here are two more clues:

1. When I turn on the game or go into switch test mode, the right bumper switch registers as closed. However, when I play a game, the bumper does not constantly fire. It only fires if the bumper switch is hit or the Bomb O switch is hit.

2. If I press the Bomb O switch and hold it, the right bumper fires once, just once. When I release the switch, the right bumper fires once again. So it fires once upon hitting the Bomb O switch and once upon releasing that switch. That seems weird to me.

Do those clues help?

Thanks. I replaced the diode, but I can try to replace the cap and see if that works. Why would a faulty cap on the pop bumper lead the to the bumper switch being triggered when I hit Bomb O?

Solved! It was the cap on the pop bumper. I wouldn’t of thought to replace it so thanks to those who chimed in. Can someone explain why that cap caused this particular problem, just for educational purposes?

Why did it only manifest itself when Bomb O was pressed and not any of the other switches?

I figured it was gremlins.

I always try to approach these things logically and feel like I'm missing something when I can't figure it out. But, perhaps the circuitry is just far more complicated than my little head can deal with.