I hear sound but no picture on lg 55le5400

Sounds like Back - light problem. Check and replace damaged component/s at its back-light inverter board, or replace this board as card basis. If you wish to get some details; check the site linked here. Surf the site with patience. Pull up older posts. It will be best to replace the inverter board as card basis.
http://electronicshelponline.blogspot.com/
To some model sets; especially LED back-lighted types; the back-light inverter circuit will be part of the main power supply board [SMPS]. In such cases, the power supply board might need replacement. To some models sets, the back-light inverter and SMPS section circuit will be integrated at its main board itself. If so; the main board should be replaced. To some models of sets, all these section circuit will be integrated at its main board. If this is the case, you have to replace the main board.

LG 55LE5400 UC AUSWLNR EAX61532702 0 Main Board

Items found similar to LG 55LE5400 UC 55LE5400 Main Board LA02D...

it is possible that either the lvds cables connecting the mainboard to the lcd panel are destroyed somehow or either the
Lcd panel itself has the problem could you provide some extra info a photo maybe so i can be more helpfull

hi it sounds like you may have a panel fault, might best to get in contact with the people you purchased it from see if they can help good luck

regards
shaun

First of all, shame on LG for not providing support on their product. It sounds like this TV isn't that old. I was just bragging on them to several people this week. Your symptoms sounds like a main board issue. But in order to be sure, proper troubleshooting will need to be done to pinpoint the problem. You will have to pay a diagnosis fee, usually $75 range, but for a 55" late model set, I would say it is worth the money. So sorry to hear this, I'm hearing so many of these late model LED TV's failing left and right.

The electrolytic caps need changed out on power supply module, or the power supply needs change out. Check at www.partstore.com for power supply.

Does this same problem exist if you're playing back a DVD?

If not, it sounds like a problem with your cable/satellite signal.
Recommend contacting your provider.

You can use rca cables to hook it up or use the toss link cable if your receiver has that.