What else could be wrong with lcd tv that has no video or audio, TCON board has already been replaced?

I think that the Tcon board with what you are talking about for your TV could be not working and needs to be replaced. It would be more cheaper to buy a new TV than to try and fix the TV that you have that is not working.

The TCON board or the LCD panel is faulty. Can confirm by replacing the TCON board .
If you wish to get some details; visit the site linked here. Pull up older posts. http://electro-medical.blogspot.com/The TCON board or the LCD panel is faulty. Can confirm by replacing the TCON board .
If you wish to get some details; visit the site linked here. Pull up older posts. http://electro-medical.blogspot.com/

T-CON stands for timing controller and it wont affect the audio. You have an issue with the main board.

Here is what the service manual says ...14 red flashes- bad TCON or Bad LCD panel, replace tcon board. unplug tcon board if tv stays on without tcon board replace tcon board.

Good luck!

TCON board or the LCD panel is faulty. Can confirm by replacing the TCON board. In some models TCON board is integrated to the panel, In such cases you have to replace the panel.
If you wish to get some details; visit the site linked here. Pull up older posts. http://electro-medical.blogspot.com/

The TCON board or the LCD panel is faulty, Can confirm by replacing the TCON board.
If you wish to get some details; visit the site linked here. Pull up older posts. http://electro-medical.blogspot.com/

Hello. Before you start replacing parts, make sure your connections are correct. It sounds like you have connected a composite source to a component input. Composite is three RCA plugs, a yellow for all of the video, and a red and white for audio left and right channels. Component is five RCA cables, green, red and blue for video, and red and white for audio. if composite is connected to a component input, the picture will be black and white with squiggly lines all through it.

Tad G chances are you installed the wrong Tconn as that model used two T con boards both look identical but they are not interchangeable the two types were part numbers 185724011 and 185713211 I can assist with determining which version you have

Don't return the new refurbish tv power supply board,keep it and used it the old one u have it in ur tv it is shorted and dead already.Return those LCD inverter boards though.Should buy a main tv Tuner signal board and replace it too though,that the other board it is causes and it is also dead too.Repair this problems many times before,alway these two boards are dead.I promise u the tv now will have stable power supply again tv will work again.

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.