I've been spending WAAAAY too much time on a clients basket case Star Trek. Game is now at least playable (rebuilt power supply, modded driver board, re-pinned J4 on the MPU, replaced bad resistor on the MPU, replaced ALL rubber on the PF, replaced all bad bulbs, cleaned plastics, rebuilt left flipper mech) but the sound board has never worked, and troubleshooting these with a DMM is not possible so I busted out my scope...
U11 has the correct signal going into the IC but zilch coming out either outputs. (you can see the input signal in the pic) I'll get a replacement this week and hopefully button this up for the customer by the weekend. (and I'll be glad to see it go)
D