failing to boot , black screen

Hi there i have a toshiba satellite c660d im having trouble with. was working fine shut down for a few weeks then tried to boot but its not booting, the fan spins up for a couple seconds and shuts down and leaves a black screen. hard drive and ram are fine tried in another laptop. im comfortable in striping down the laptop and computers but im stumped on this one. ive dissembled the laptop and checked all connections and ports cleans fan and everything inside but still no luck. ive tried the remove battery and boot from mains power and the shift f8 and the 0 but still no luck. i think its either a screen error as ive yet to try an external monitor but i have check all connections on it and there fine or something is shorting out the board. any help or advice would be grateful.