Yes, the push button on the main CPU board. Hold the button down, power up and continue to hold the button down for 2-3 seconds after powering up. You'll typically hear the door coin divertor solenoid pull in, the pull handle solenoid may pull in and the sound amp power up.
Loss of the battery voltage to the RAM shouldn't prevent the board from starting up. Loss of VCC (+5vdc) to pin 24 of the Ram chip will though.
Since the resistor R27 was removed when the board is powered up the voltage on the battery should remain the same, about 3-3.6 volts, if there's more than 3.6 volts then the switching diode D5 could be shorted.
The 9.5vac pin 8 will be close to 5vac when measured to the DC ground pin 7. To get the actual 9.5vac you'd have to measure at the power supply transformer taps. If there's 5vac at pin 8 you're good.