On off switch does not work somtimes set goes on and off comes on with sound but no picture un plug it and sometimes it works fine

I,
Well basically Sam sung most common parts that go out are,
LAMP: The generic lamp will go from 3500 to 4500 hours and a Phillips lamp will go for 6000 to 8000 lamp hours,
How It Works The lamp itself typically uses AC current and about 15,000 volts to ignite the lamp's mercury vapor gas. The gases inside the lamp react when electricity charges up the mercury gas creating very bright light. The voltage drops to keep the flow of electricity to the lamp. The lamp works with the ballast to project light into a light engine that separates the colors of the light, then recombines them with an image. The image is then reflected on the back of the TV and then onto the screen. But you need to listen carefully for any strange noise like (CLIKING,HUMMING,BUZZING,WHIRLING SOUNDS) that will help you narrow down whats is wrong with your TV because the BALLAST witch is the board in charge of sending the correct amount of current to your lamp could be weak and will not power up you will hear a clicking or electrical humming Also the color wheel is a common part that goes out on Samsung and that will give you a vibration and a loud whirling sound,you can get more help and real good prices at http://www.discount-merchant.com/?click=52978 good luck and keep us posted