Quoted from Pacer:
The game is malfunctioning and it seems pretty clear its the switch matrix/lamp matrix. Lamps all seem to be operating fine. In the switch test, when the tournament switch is turned on (strobe 0, return 5), all the switches connected to return 5 also trigger. When the tournament switch is turned off, the switches of return 5 don't improperly trigger.
Ok, more info. It seems that triggering any switch in strobe 0, also triggers every other switch that shares the return with the intentionally triggered switch. Research indicates that this means that strobe 0 is shorted. However, the lamps are operating appropriately. If strobe 0 was shorted, I'd expect it to also monkey with the lamps.
If I remove the strobe connector (A3J3) and both the lamp return (A3J4) and the switch return (A1J5) from the board, and jumper appropriate pins on the board to trigger switches on strobe 0, the issue persists. Thus, I'm interpreting this to mean that the issue is on the board.
Furthermore, if I run the game with the lamp returns disconnected from the board (A3J4), the issue persists.
The issue doesn't seem to be present immediately upon startup, but then shows up pretty quickly in a first game.
With the board removed, Q33, the MosFET for Strobe 0, tests just like every other of the transistors Q33-44. Seems fine.
Now, as I stated, the issue isn't initially present on startup. Accordingly, it seems that my testing of the board may be simulating the startup when the issue isn't present. I'm not sure if the transistors are prone to failing under stress and having the failure go away when not in use. I've don't recall hearing of such a thing.
I'm not sure what to look at next. Clay's guides don't really go any further into potential board level issues. I'm not sure how to test chip U8, which drives Q33.