My Vaio all-in-one JS just went dead yesterday and

~ Condensation = You might need to unplug the AC Power and the Power from the wall. Wait about (approx. a day [if it's bad] or an hour). Replug back, see if it works.

~ Did you add or remove any components to the computer? If you did, revert it to normal.

~ If you recently plugged into an external monitor (like a projector or tv). Plug it on your computer and check if it works.

~ Make sure everything inside the computer is working normally.

Those are my 4 suggestions, if those don't work, let me know ASAP.
Good Luck!

HT