I’ve been getting handy with a multimeter now, and it looks like the voltages are all getting to the right spot on the pinball displays, but the displays still aren’t working. It appears that having dead displays isn’t that uncommon. So, it looks like I need to either (a) buy 2 new alphanumeric displays and do quite a bit of unsoldering/soldering to replace them, or (b) get a board designed/manufactured by a third party that uses LEDs instead of gas tubes and replaces the entire existing display board. I’m currently leaning toward (b), because even though it’s about twice as expensive the LEDs should last much much longer.
However, I need to find a place that carries the model for my type of machine. The online stores that I’ve found seem to be out of stock.