short the pins of the power button together only momentarily. If the pc does not come on then you have a motherbd or power supply issue. You can the short the green wire on the large 20 or 24 pin motherbd connector from the power supply to any of the black wires right next to it. Leave the jumper in place. If the pc boot up now then you have a motherbd issue. If not it could still be either or both and you would have to test the psu manually or test the motherbd with a known good psu.