How did you recharge the displays?
Taken from Clay's Pinrepair guide.
Recharging System1/System80 Score Displays.
The six digit blue Futaba score displays used on System1 and System80 games are
identical and interchangable. But often the displays will fade over time, eventually
not working at all. There may not be any problems with the display circuits
themselves, but instead there may be oxidation on the display glass filiment wires.
There is a trick to burn this oxidation off the filiment wires, making the displays work
like brand new (there is a limited number of times you can do this though, the law of
diminishing returns does apply).
First turn the game off and remove one of the 6-digit score displays. Then take a
pair of jumper wires, and connect them to the front door coin lock-out coil lugs (24
volts DC). Next attach the aligator clips to the outside most pins of the score
display (it does not matter which gets ground). Now turn the game on for 3 to 5
seconds, then immediately turn the game off. While the game is on, the thin
horizontal filiment wires in the score display glass will glow. This burns the oxidation
off the filiment wires.
WARNING: Do not leave the power to the display for more than 5 seconds, or you
could burn a filiment wire ruining the display! Also do not use coil voltage to recharge
the 4-digit ball/credit display. If you need to recharge a 4-digit ball/credit display,
use 8 to 12 volts DC instead. I have even heard of some people using a 9 volt
battery to do this.
