My LG 50PB690V plasma 3D TV powers up with picture and sound. After a few minutes the picture turns itself off leaving the sound working ok. This process can be repeated.

SOURCE: TV turns itself off after a few seconds, no picture at all

Sounds like the typical Flyback and shorted horizontal output transistor. Problem is the transformer is NO Longer Available

SOURCE: 42 inch LG Plasma TV Lost Picture

Hi it sounds like it has had an elctric fault like a resistor failing.
The click you heard would be a internal switch that cuts off the elctric supply to the screen to stop furthe damage hapening.
It could even be something simple like a bad solder and in that case will need locating and resoldering.
How old is the telly and how often is it used.
When you switch it off leave it off for about an hour then try again if you have allready done this then it probably is a blown resistor are you sure nothing has been pressed on controll have you tried seeing if you can acess the menu screen via the remote and see if that comes up on the screen let me know ok

SOURCE: TV turns itself off after a few seconds, no picture at all

As far as fixing goes, you might as well get a new TV... Unless its a LARGE EXPENSIVE HOLY $%^# TV, It will cost more to fix, than to just buy a new one, unless its under warranty, which being an older model as that (or so im reading) It may not be covered.

Try unplugging the TV, and while unplugged, hold down the power button for a full minute (yes, with the plug NOT in the wall) after a minute, plug it back in, and try. Its a hard reset. If it still does not work, and you've tried different outlets, It's probably a repair issue, and you'll need to get someone to fix it, or just junk it :-/

SOURCE: LG 50" plasma tv

call 877-543-8325 this is an LG Executive call center and they will fix this for free. I have a 50" plasma I bought january 2006 which is out of warranty by 5 months. They faxed me and the LG repair shop a 30 day warranty for my tv to cover the repair. Just tell them you heard a pop and in my case the picture is distorted. All they need is the model number and serial number and they should take care of it. No arguing needed.

SOURCE: TV Picture Goes Black

I had the same exact problem.
I removed the bulb and cleaned it. There is a small screen at the top of the bulb and it was covered with dust. Once it was cleaned I replaced the bulb and it solved the problem.
Thanks to those who posted the solutions