I'm working on a WPT that I just picked up with a strange light matrix issue. There are a few lights that are all contained on row 10 of the matrix that get really bright during gameplay during certain light sequencing. The lights on that row also trigger at various times during the game married to other lights but don't appear to be directly triggered by the other light when I go thru the single light test. I suspect that it might be a board problem since I've traced the problem row lines on the harness and didn't find any issues, backwards blow diodes, shorts etc.

One weird issue is that when I put the game in test mode and just test each row, row 10 will stay of for every row, but when I hit row 10, it activates row 9 in test mode. Row 10 will not activate row 9 during test mode though.

Unfortunately I don't own another game or have access to a stern game that uses these particular rows to make sure. I tried it in my buddies Metallica but realize that it uses LED boards so the test was inconclusive. Anyone have any advice on where to check. I can write up the matrix in more detail and scan it in if that would help because there are some odd combinations happening when doing the single light tests.

Ok, I typed this earlier at work and was trying to do it from memory so I wasn't very concise. So here's the issue. The four lights at the bottom of the playfield - Play the button - Know your Outs - spot the tell - change gears all glow extra bright during game play. So when I run the matrix thru the light test with the columns everything lights correctly in its respective row. The four lights I mentioned above still glow extra bright when their column is active.

When I run thru the row test, Row 10 is active the entire time almost as if the transistor is shorted on.

Here is where it gets really odd and confuses me, when I run the single light test it doesn't appear to have a pattern in which lights activate other lights. The only real consistent clue is that everytime you activate a single light in column 3 regardless of the row, it lights the corresponding light from row 10. I'm going to post a picture of the lights that activate together when doing the single light test. Basically I went thru light by light and if a light in the same row activated I highlighted it. So any light that is highlighted in the same row mean both of them were activated when cycling thru the single light test.

tmp_20140224_200229-964183359.jpg

So I pulled the row connector off the board and am measuring a diode drop of 1.3v from ground to the pins on the harness. Would this signify that I have a ground short on my row light matrix? It has the same drop on every single pin that has a wire.

Ok I can do that. Basically I was trying to see if there was some sort of clear pattern. The circled lights were when I was running the row tests and I was checking off to make sure that row 9 and 10 were both activated at the same time. The blue highlighted lights were when I was testing the single lamps. So when one pair was activated, left VUK lock was also activated.

I pulled the row and the column connectors and tested each one against the other and I'm getting a proper diode drop except on a few that have LEDs in them which was higher, but I'm attributing that to the LEDs. I'm also not seeing any shorts when I measure each row pin to ground and each row pin to each other row pin. I performed the same test with the columns measuring to ground and then to each other row pin and didn't see any shorts. It turns out when I saw the 1.3v drop earlier I still had the column plug on the board so I was seeing a diode drop from the drivers.

If I had a short in my light matrix, wouldn't it show up when I measured it against ground and all other wires in the matrix?

I'm starting to think this is a logic error on the board. Unfortunately I don't have another machine that has as many lights as this game to verify.

On a side note. This is really driving me nuts. I rarely find a problem I can't fix and I just don't see the pattern with this one. I might have to step back and diagram it out better and then I'll see it.