There's no voltage regulator. But the same power supply powers the whole thing, monitor, marquee light, and the PCB, unless I just don't understand how it works exactly. Before I checked the voltage by unplugging the JAMMA harness everything worked, besides the visual noise I was trying to get rid of. Now the PCB seems to not be working and the LED won't even come on. So hopefully this is just a PSU problem and the PCB isn't messed up, right?