My LG tv (had since Nov) says no signal for the tv...
Try unplugging all inputs and the power cord from the TV for 5 minutes. This will allow the main board to reset.
Next, just plug in the power plug to the TV, power up the TV, and even though there is not a source connected to the TV, check at least three inputs and see what the TV will report on the screen for each input.
Next, turn off the TV, plug in all known working devices (Cable/Antenna, DVD, Blu-Ray, Cable/Satellite box, Game, ….) with a known working cables to the TV, make sure all the devices connected to the TV are powered up and on, and now power on the TV.
Now check to see if the TV is seeing valid signal for all the inputs connected to the TV.
If your TV cannot see any signal at any of its inputs (HDMI1, HMDI2, HDMI3, AVI1, AVI2, Component1, ……), then the main board has failed and need to be replaced.
Good Luck.