I have been working on a friend's Laser Cue - Williams System 7. It had not been used in 15 year and had/has a lot of issues. I thought I had fixed many of them by working on the boards but now I have hit a setback and need to go back and start over. I originally tested the Power Supply by pulling off connector 3J4 and checking the voltage of the pins. I got -36.8 DC volts on pins 1-4 and 9-12 and I got 18.9 DC Volts on pins 5-8. The picture shows what I believe this connector does. Though I am far far from being an electronics expert, my thought is "Well they are only grounds so the voltage numbers do not really matter." Right now when I turn on the machine - the GI lights go on, the Diagnostic Display on the CPU shows a 2 and nothing else happens - No playfield lights and nothing on the displays.
My questions are: 1) What could cause the voltage drop on the pins on 3J4 and would this voltage drop have anything to do with the game not starting?
2) What else can I check on the Power Supply Board to make sure it is not the issue?
Thank you for any help you may have.

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