My TV's backlight isn't functioning correctly how can i fix it?

SOURCE: i think my tv has screen damage but i dont know

replase the part called P T C .

SOURCE: Blue screen with red key in bottom left hand corner

The Tv's Child Lock has been activated...
Hold down the F button and press the MUTE button to unlock.
You can only remove the child lock using the remote.

SOURCE: unlock apex tv model # AT2702

• If you have a blank screen with a red key on the bottom left, simply press the (function or F) button and the mute button at the same time. This will unlock the screen and allow you to view the channel as desired.
  
  
• If your TV asks for a 4-digit code or password please enter 3308 or 6688 to unlock the screen or reset any preset rating levels.
  
  
• If you have a GT2011J or GT2011S Television, hold the (Display) button for 10 seconds, it will unlock the screen. If password or code is requested, try 3308 or 6688.

SOURCE: Help! Turned on our tv and all there is a blue

Somebody put a lock on it. LOL There is several keys you can press together in all TV to go into service mode, I don't remember the one for that particular model. See if you can find it on the internet. Look at one of those television case history site. Some are free. Be carefull you don't adjust anything once in the service mode!! That is actually used by technicians only. A consumer would not have a clue what they are adjusting.

SOURCE: TV HAS LITTLE RED KEY AND WONT DO ANYTHING

my t.v is lock