Unplug the power cord and then unplug the 24 pin connector to the motherboard. Plug the power cord back in and using a basic testerj ust one with a light that comes on signaling power is flowing. You do this by clipping the aligator clip to bare metal on the chassis and take the other end and touch the individual pins one at a time on the 24 pin connector from the psu. If the light goes on in the handle of the tester , you have power. Repeat this process for the rest of the pins until you have done all of them of 1 or more pins don't light up the tester, then you have a bad psu and need to replace it. If they all show as having power, then the psu is good and you have to do more testing with the rest of the hardware. However it is likely the board is dead and needs to be replaced. But before you do anything, you should check all the connections particularily the power connectionand make sure everything is plugged in properly. Goodluck.