I have 42 inch flat screen phillips lcd tv that is 2.5 years old with no picture but has sound. Any ideas?

Hi joeflick,
Power on the unit in the dark room then shine with the flashlight directly in the screen, you will barely see the images. This is because your backlight is not functioning. The following reason is the caused.
1. Power supply - missing B+(supply voltage) coming from this board feeding the inverter board. This is caused by faulty transistor, dried/leaky electrolytic capacitor, open fusible resistor.
2. Inverter board - even the B+ is good from the power supply, if the fuse, driver transistor, driver transformer is faulty no output to the backlight resulting to black picture.
3. Busted backlight - even inverter board is good but if this is busted resulting to black picture also.
Diagnosing the fault is technical and if you don't have necessary tools and test instrument and can't fix it yourself, I would advice you to look for an experienced technician to isolate the problem.
Hope I helped you.
Have a nice day!
Thanks for using Fixya.