Thank you for posting your question on Just Answer! I will be happy to help you with this problem. Can you please give us some more information so I can better answer your question.
How old is the set?
Has any work been performed?
Can I have your model ?
this is a very simple approach.
(Please click on high lighted words)
First push the menu button with the sets remote and if nothing comes up then
Friend this is a very common problem with LCD and also DLP within the power supply the capacitors
Start to fail and the way you can tell is to check them visually for swelling or expanding of the top.
It will be easy to see the bad caps will not be as flat on the top as the good ones, But also you can have a bad resistor or diode and even a bad regulator. Would like for you to take your meter and place it on DC voltage the positive end on every connector that says a voltage and the negative wire to the panel this is the best ground. Turn on and see if the unit tries to climb, If you don't find one that's trying to climb, another method is to locate a short circuit, place meter on ohms or beep test follow same procedure no voltage should be shorted to ground. And this is the problem,
Exchange them and you will be ok, Well good luck friend. And if it doesn't work make sure the power supply is sending 24v to the inverters when you turn the set on your meter should climb but won't reach 24v because unit will shut down and if so we ruled out the inverters or backlight I seen this problem also caused by the signal board it has a power on command missing and it looks like the power supply is bad but actually it's the signal board, it may be labeled on the board a active high or low 5v which sends the command to the power supply.
Good luck friend, and if my efforts are appreciated, feedback and or bonus will be appreciated
Capacitor pictures inverter pictures... cold spray can be used if your set works for awhile then shuts down.