Hello, need some help on a switch matrix issue.

I powered off the game and proceeded to adjust the pops. I clearly didnt wait long enough as this blew the ULN2803. Luckily, it is socketed, so i replaced the ic chip and Fuse at F115. Switch matrix works and I can start a game, but have column out.

The column runs the pops, slings, and Left 3 target bank. Its associated with U20.13 -- which I believe is the ULN2803 I just replaced. They do not appear as closed in the switch matrix. Any ideas? Did I fry another chip?

I checked all fuses on Driver Board. I can fire all the associated solonoids in test, but no switches. Any ideas would be great help!

BSD Switch Matrix (resized).PNG

Good thought. I just checked. All the wires pass the tug test on the switches and they are attached. Also checked continuity between them all and good. I had a very tough time checking continuity back to the board, since the connectors are so small. But I think I am good since I didnt touch any connecters on the board prior or after the issue. Only contact with the board was pulling and replacing ic socketed chip. I did monkey around with the pop bumper switches, but as I said, I am covered there.

Is there a way to test the U14 chip? I don't have a logic probe.

Quoted from maestro:

Have you tried putting the game in switch test mode and pulling J207 and J205 then putting an alligator clip or otherwise making a connection directly from J207-6 (column pin) to each of the pins on J205 one at a time? If the switches register like this your board is fine. If they don't register then you've got board issues. Its a quick way to eliminate the problem from the board or the wiring. Double check those pins and plug numbers I mentioned. The picture is a little blurry.

Did the test and confirmed issue is on the board. No switch registering on that column. First time I have ever done this test, always a little afraid of alligator clips and shorting something making it worse, but the test was easy. Glad to learn how to do this.

So - I am assuming next step is to target the U14 chip?

Thanks to everyone that offered help.

I ended up buying a logic probe. A little intimidated on how to use. But i found this link to a youtube video in TerryB's logic probe thread and this video demonstrated exactly how to test the U14 chip.

» YouTube video

I confirmed the chip was bad with the logic probe. But literally seconds later I think I shorted between 2 legs of the ic chip with the probe. This caused the game to reboot. Luckily I didnt damage anything else, but I certainly finished off the (already bad) U14 chip.

So I was able to cut out the chip, put in a socket, and replace. All is good again now with the game. I learned alot from this little issue. I don't recommend using a logic probe on a board while it is still in the back box. Those legs on the ic chips are literally a millimeter apart, so it seems crazy easy to short something whilst reaching in there. I have pretty steady hands, but so easy to short something.

Thanks again from the help. And thanks to TerryB's logic probe thread and the video Chris Hibler put up on youtube. Hope someone can learn from my errors and my fix in the future.