Unscrew the three screws on the bottom of the frame and remove the back. Look at the 25 capacitors on the motherboard. Examine the cans for corrosion and/or bulging. Look at the 4 LED lights at the middle of the motherboard and see if any are on. Just to the left and down just a bit you will see a reset button or two hit them. You may see a reset button on the power supply, hit it. Examine where the cords enter the power supply from the motherboard and look for a burned or darkened area. Let me know what you find so we can proceed. Thanks for coming to iFixit.