The specific type of hardware failure can be determined by a "hidden" error code
Turn the xbox 360 on, and wait till the 3 red lights are flashing.
Press and hold the sync up button (the small white one), while holding that button press the eject button.
The LEDs will now blink the first number in the code (as described below).
Release the eject button and press it again.
The LEDs will now blink the second number of the code.
Release the eject button and press it again.
The LEDs will now blink the third number of the code.
Release the eject button and press it again.
The LEDs will now blink the forth number of the code.
Release the eject button and press it again.
The LEDs will go back to the 3 red flashing lights.