With standard Jamma arcade boards the general rule of thumb is get an adjustable arcade power supply and a digital multimeter and set the 5V out to 5.1V. That will run 99% of Jamma boards including every SF2 I've ever tried. Some huge boards need more, like Midway boards from the 90s that supply power into hard drives and a lot of IT boards sucked the power too, and stuff like System 246. Those might need 5.35 or so, but use that info at your own risk.
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