Quoted from Gattiman:Well I’m about 10 hours into this hell of a problem. Also noticed my upper playfield came broken at the back corner. JJP has been about as helpful as a hole in the head. I’m thinking the main board is just bad. Traced the wires all the way up to the monitor and nothing is wrong. I’m tempted to just tell JJP to come get it what absurdly terribly QC.
Put the game in matrix switch test and press enter to bring up the grid full screen. Find the plug for that opto pair on the opto control board - assuming you are talking about switch 78 upper playfield VUK - it should be in the green socket in position 6. Unplug it from there and move the plug over to the blue socket next to it (which should be empty if you have an LE) - plug the opto pair into that socket instead. Does the game react? Does the box for switch 79 in row 7 change color? If the game recognizes that opto pair in the blue socket, then chances are that the opto pair itself is okay. If it does not, then the opto pair itself may very well be the problem. You can try it in a couple of other spots to make sure.
Next would be to take a known good opto pair from somewhere else on that board and plug it into the green box at position 6? Does the game react accordingly with a known good opto pair plugged in there?