15-inch Phillips LCD FlatTV

It could be the AC adapter. That is easy enough to check with a DMM. Turn on the meter, set to volts dc, push red probe into the hole in the output power jack and touch the black probe to the outside of the same jack. Have someone plug the AC cord into a good outlet(one you know has power). If the adapter is working you should see 12 vdc displayed on the meter. There still could be a problem as I recently found an adapter which displayed the correct voltage with no load but little or no voltage with a load. Testing with a load is a problem if you are not familiar with the procedure. Odds are if you have 12 vdc the adapter is fine and you have a short somewhere in the monitor. If you are handy with tools and feel confident, remove the back of the unit and check the fuses in the power supply. If they check OK you probably can't do much more. Unless you are an electronic tech you will need to take the unit to a shop for repair by a qualified tech. Good luck.