Sadly, other than re-plugging everything back together in case it was just a dirty r loose connection without a power supply to swap-out as its often the issue. Your next issue is replacing the [guide|3162|is replacing the PRAM battery] if you tend to leave the system unplugged or have a power strip which kills the power (loose vampire power). The last effort is a good inspection of the logic board for discolored or damaged components.