Strange switch issues happening on my friend's Road Show which I could use some help diagnosing, please.
Most of the cabinet switches don't work (slam tilt, coin door closed, buy in button, always closed, start button, plumb bob tilt). The flipper buttons and coin door service buttons are all OK. The affected switches are connected in the matrix (13, 14, 21, 22, 23, 24) but I think this might be coincidental. Not sure it is a matrix issue because switches 11, 12, 15, 16, 17, 18 and 25, 26, 27, 28 all work. Switch 24 (always closed) shows as open, but no errors show up on the display relating to this (I would normally expect a 12v error if switch 24 was open but this doesn't happen).
As it is affecting the cabinet switches which are run through the coin door interface board, I swapped this with a working one first. No change. Then I swapped the MPU. No change. So problem is definitely in the cabinet somewhere. While examining the switch wires on column 2 I found that I have continuity from J212-2 (green-red) on the MPU to the non-working switches (i.e. switch 21-24). The only anomaly I detected was someone had run an extra wire from Red's mouth (switch 25, working OK) and spliced it into the green-red wire connecting the coin door interface board to the buy in button (switch 23). I removed the wire to no effect. Suggests to me that someone had tried to reconnect column 2 to Red's mouth switch to fix an issue in the past. But I can't find anything else anomalous in the cabinet. Connectors and wires look intact.
Not sure where else to check from here. Any advice is appreciated.