Long story short, I have a machine that I tried to re-do the whole wiring harness on, and must have messed up seriously. The flippers weren't working, so I took another flipper board and put it in, and did some serious damage to it somehow. Now, whatever machine I put it in, vertical lines appear on the DMD, in a pattern like I II I II I II I II. Also, all the flippers lock on. I'd like to fix this board, even if it'll take way too much time/money to be practical, as a way of better understanding wpc flippers and data lines. The schematics booklet is not very helpful, because it has many places where a chip is marked u?, or lines just kind of vanish into thin air. So to start, can I assume the problem lies in u5 or u2, as only those chips make use of the data lines?

Sorry, WPC fliptronic II. Shoulda mentioned that. It was from a whitewater, stuck it in a shadow, blew it up, now it's living in a TZ. If I don't connect the ribbon cable to the board, the DMD is fine. I'm completely sure the problem lies in the fliptronic board, and no other board, as I can stick in another flipper board in the TZ and everything is fine.

Oh wow. Pins (on u5) 6,7, 9, 11 and 12 have readings like a tenth of what they should be. So that's a major sign that it's bad, I assume. Can you do that with all chips? What exactly am I doing measuring that? Thank you john, you're totally helping me understand this better.

Cool. Thanks muchly.