Zend certified PHP/Magento developer

Sony Vaio Blackout Display Issues, screen/monitor tested today and seems to be right, what else could be the culprit?

Symptoms:

  1. Since two weeks display used to suddenly disappear and then when it comes back the brightness used to be 100% scaled automatically.

  2. Now the computer is booting, the fan’s voice is there, Keyboards caps Lock is showing LED ON/OFF, but permanent blackout.

I took the machine to the local vendor he tried to troubleshoot the initially blamed the screen, but he tested with 5 screens none worked, which means the issue is somewhere from the motherboard.

Which steps should I take now? which hardware components should I suspect?