LG 47LC7DF screen is black

SOURCE: LG LCD TV 32LC4R BLACK SCREEN

same here How do you change the Power regulator?

SOURCE: LG 32LC2R - No Picture Sound Ok

Hello
It sounds like there may be a issue with the inverters on the Lcd panel, yes you will need to contact a repair center.

Steve Allison

• 5569 Answers
• Posted on Sep 14, 2008

SOURCE: 47LC7DF

When problems arise that kill both video and audio, it is normally related to the failure of the main power supply.
Nearly all modern electronics uses a 'switched mode power supply.'
They are more efficient while being much more complex and prone to failure but offer the added benefit of being designed so a 'downstream' fault will cause the supply to shut down to avoid setting fire to your home.
The supply itself will also cycle if it has an internal problem; once again, to prevent destroying itself or anything dependent on its outputs.
 
Supplies built a couple decades ago could only do this by blowing a fuse and there are conditions that can occur that would not blow the fuse but would allow overheating and further damage as well as fire.

You might try the following: Pull the AC plug from the wall and ignore the set for a day or overnight, then plug it back in.
There are literally millions of semiconductors in a modern TV receiver and sometimes, they trip and lock themselves up.
When that happens, removing all power from the unit will allow everything to return to a stable state and function as designed again.

If that doesn't help, I hope your set is still under warranty as this could be a multiple hundreds of dollars to repair.
The power supply is often on a separate board and unfortunately, component-level technicians aren't that common anymore so frequently, the board is replaced and the old one discarded.

SOURCE: LG 42LG5 TURN ON TV PICTURE GOES BLACK

This could be 1 of a few things here. Without opening up your set and trying to look at voltages or indiciator lights I couldn't tell you exactly without some more info.

Without looking at it myself here are my thoughts and where I would first look at.

It may be a main board because:
1) Main board processes all your audio/video signals. Bad main board means bad video processing. Could do that. Especially if the main board is not sending the right signal or a bad signal to the rest of the boards so they don't do their jobs. 

It may be a power supply because:
1) Power supply is well, the power supply. If it's sending inadaquete voltage to the main board you may not be recieving enough juice to keep that main board doing your video processing or further up the line keeping enough juice flowing to your TCon board to keep it telling things where to go and what to do. The power supply sends voltages to your Ballast board(controls your lights) and to your main board through which power is supplied to your TCon board via a LVDS line and a +12/+16V signals. If the power supply isn't pumping out enough juice to keep the TCon or Main Board running, it could be a problem. By the same token it could be that your P/S isn't sending power out to your ballast board. 

It could be a TCon because:
1) If the TCon is bad, you won't get your pictures. This could be the TCon board itself or the LVDS cable from your TCon to your Main. However, with few exceptions, if it's a bad TCon you're looking at a total panel replacement. 

It could be a ballast board because:
1) The Ballast Board controls the lighting behind the LCD screen. If this isn't working right you won't be seeing much of anything without that back lighting. If this is bad, it's a panel replacement. These are not field replaceable items by LG. 

Based on the symptoms, without more data or a eyes-on view of it, I would say you're most likely looking at a Main Brd or PSU problem. 

SOURCE: lg tv cycles off and on non-stop

check for the suppy it may cuase of a low power supply /[email protected]