Well the tv come on but there no sound and when i try to change the source button to any funtion the red light come on but the tv is still on and if i swhich back to tv the red light goes off and green is on so how do i get the green light to stay on when i change to the source to watch my dvd player and get sound

SOURCE: Tv turns on green light blinks three times then TV turns off

Ur power supply board is dead.Tries websites Shopjimmy.com,Ebay.com to buy a refurbish power supply board for the replacement.

SOURCE: my lg plasma tv stays on standby

is you already change the power board,is possible
your y board is out...is a big board on the left side of the tv

SOURCE: No Sound, No Picture on LG 42LC7D

I do not have a solution but I have the same situation with my tv

SOURCE: My LG Plasma 42PC3D turns on and off repeatedly. I

Your plasma TV has a power supply 6709900019A. These power supplies failed due to defective capacitors. See the picture below and check the capacitors mark with the red lines. There are 10 capacitors that should be replaced even if they do not show signs of bulging/swelling on top.
The value of the capacitors is 3300uF/10V but you can use 25 volts as long as they fit in the space provided by design.

SOURCE: My LG 50PC5D has a hard time turning on. when

Hi,
It seems issue with power supply board and most probably few electrolytic capacitors are dried up and causing problem.
Qualified local tv repairman visual check is needed to confirm the reason of problem as he will test/ check output volts of power supply.
If this tv is 3-4 years old then problem would be in power supply board as mentioned above.
Let me know if you have additional question.
Thanks.