1st u must determine what is running:
# Is the drive LED blinking when powerng on? If not, either the drive is bad or there is power problem.
# Is the drive LED blinking for a short time when powered on then stops? If so, the drive is doing its POST, but the CPU isn't running. Could be a bad CPU or other support circuit.
# Is the drive LED blinking relatively continually? If so, the computer is running but there may be a display problem or a bad device connected to the computer. It may also be a bad internal USB chip. I had that once.
# Is everything disconnected from the coputer except essentials?
# Have you done the flashlight test on the display?
# If you got this far, these computers tend to self disconnect the display cable. You may be able to just remove the KBD to get to it. Search for your "[model #] service manual" to find directions.