Yes, checking for the proper voltages at the power supply is always a good idea. You can unplug the cpu board from the power supply for testing.
You should be able to find exact pins for voltage in the manual.
3J2 should have +100vdc, -100vdc, and +5vdc for the displays
3J1 should have +5vdc, +12vdc, and -12vdc
Check out pinwiki, as I'm sure there's more detail there too.