looking at the schematics the -30V test point is on the High Score Memory Circuit.
"A11 produces a 0-15V square wave at a 1V rate. This signal when +15V forward biases diode CR5 and allows capacitor C86 to charge to -29V. When the signal is 0V, CR5 is cutoff and CR4 is forward biased which causes C84 to develop a charge. C84 charges to approximately -28V. This is the potential required for EAROM C0 to operate."
doesn't really mean anything to me, i figure if the high scores are not saved then it could be a problem.
i'm sure it should be ok