My IJ was working perfectly before my son and I decided that we would put in some new LEDs that we just got. After placing the LEDs we put the glass back in and got ready to play anther game. When we started a new game the gun would not "fire" the ball. There was no "gunshot" when the trigger was pulled which means that the switch in the gun was not being triggered. When I tested the switch in "switch test mode" it was not registering. So my question is is there a way to test the switch itself, like with a voltmeter or something? Is there something else I could be missing? I have no idea how changing out the LEDs on the playfield would have caused this problem but I was working perfectly until then. Any advise you can give would be much appreciated.

Wires are attached to the COM and NO. There is a diode attached to the COM that then attaches to the wire. What will I see on the meter when it closes? Which setting on the voltmeter is best to use?

The idea that another switch might be killing it is a great one--are there certain switches that will kill it that I should check first?

So I looked at all the switches that were in the same column and row and all of the switches that are in the same column are out. The switches that are on the same row are fine. What does this mean? I checked all the connections at those switches and the only thing that I see that does not seem as it should is the the left jet is connected to the right jet by the jumper wire that is seen in the picture (it is the white wire going from one switch to the other). The switch matrix states that each jet should have its own green-orange wire (as can he seen on the left jet switch. The game was functioning fine with this is place so I am not sure how that would cause a problem.

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I bet it is U20. I was changing my GI bulbs and I did have the power on. Newbie mistake. I had never read not changing out bulbs with the power on. I guess it can short out against a coil. Is changing the U20 chip difficult?

It's the stock board--the WPC089. It looks like it is soldered in. I guess this is not something that I should take on then. Do you know anybody good with boards that I should contact and send this to?

Thank you, I have reached out to them.

I will apologize in advance for these questions as I am sure that they are simple for anybody with even the most basic knowledge of a voltmeter.

When I am checking with my meter, I would place one probe on the wire from a switch that column has in common and the other probe where? Which setting on the meter? Do I need to activate the switch? I know that the switches are daisy chained together so is it better to the last switch in the daisy chain? How will I know if the wiring is okay vs if it is what is causing the problem?

I am almost sure it is the chip at U20 given that it is the chip that controls switch columns and all those switches are out but I just want to make sure before I get the board off and send it away to get repaired.

I certainly will. I am going to rename it as "Switch matrix column out on WPC-89 board" as I think my current thread name is not indicative of the problem. It seems that what happened is not uncommon as I have read from different sources and hopefully can consolidate some good information so that LTG doesn't have to walk somebody else through it.

Yes, sorry for the delay in follow-up but I have been so busy with work and trying to get my JP machine up and running. So I fried the chip that was in the U20 position on the CPU board. That chip specifically controls the columns of switches in the game. All of the switches in the 3rd column on my IJ were out. This occurred after I changed out incandescent bulbs to LEDs with the power on--they (the switches) were working perfectly before. Many of the bulbs I was changing from below the playfield, having to unscrew the socket, removed old bulb, place LED, the re-screw it back into place. I did all this while the machine was on. Big NO-NO unless you want to potentially fry a chip on your board. Of course, before I knew what the problem was I had to figure out if it was a problem at the level of the playfield as the switches are daisy chained together or if it was at the board. To figure this out, I created a jumper cable--a cable that has alligator clips at each end. I looked up the switch matrix layout for the IJ machine. I unhooked the wires going to the "rows" and "columns" part of the CPU board. I put the machine in test mode--specifically switch level mode--it tells you which switches the machine is reading. Being that I disconnected the "rows" and "columns" wires coming from the playfield, only a few switches showed up during this test mode. When I would hook the jumper cable to one pin on the "row" and one pin on the "column" it would show up on the test if the board was reading it--each switch has a corresponding row and column as outlined on the switch matrix in the Operators Manual. The only switches that did not show up when tested this way were the switches in column 3, meaning that the board was not recognizing any switches from column 3 which meant the chip in the U20 position was fried.

I contacted Chris Hibler, e-mailed him my problem. He told me he could fix it quickly and fix it quickly he did. He put in a socket at the U20 position and a new chip so that if I am a bone-head again and burn out the chip I can replace it easily.

Much thanks to Pinside, especially LTG, and Chris Hibler.

Please, should anybody run into a problem like this, feel free to send me a PM. I can likely help in more detail than I have outlined here.

So, in summary:

1. Don't change out lights below the field with the power on. For that matter, probably not wise to do any work below the playfield with the power on.
2. If you did and you are reading this post and several switches suddenly went out, it is probably a fried chip on your board that you fried/shorted out when you were working on the machine with the power on, especially below the playfield.
3. LTG is a bottomless pit of knowledge and selflessness.
4. Chris Hibler is awesome and fast at board repair. Very nice person to deal with.
5. If I can be of any assistance, please let me know.