No back-light on LG LED TV

1Check power board capacitors if swelled then replace them ,
2 check led output voltage at connector on power board. If voltage down come back from led penal then one or more leds fused.
Please replace it.
3 it may caused power board defective too.

This is a LED TV so there won't be an inverter board, they're only on LCD sets, what is wrong with your set is you have shorted LED lamps in the panel, its a common issue with this model TV, Ive replaced dozens of them in the last couple yrs, its not a fun job to do as the panel can be damaged very easily if extreme care isn't taken when handling it, watch some youtube vids to get an idea of how to do it...Good luck!!

LG TV 47LN5750 Backlight Out

you can get replacement parts at:
Lg 47LN5750 UH TV Parts

The backlight is not working. Either power supply or led's

Follow the link pleae. TV Boards Buying Guide

Faulty the backlight
It is necessary to remove the panel and replace defective LEDs

Best Regards!

Hi Richard, The link below is a YouTube video showing how to fix a Samsung television NO picture GOOD sound, Also there's videos down the right side of the link that may help as well........CHEERS..
https://www.youtube.com/watch?v=Bf5T2wwtydY
LG No Picture Screen Flash 47LN5200 47LN5400 47LA6200 47LN5700 47LN5750...

Fault to the main power supply regulator section. Either it will be a separate board, or the part of main board. Check and replace damaged component/s at its main power regulator [SMPS] section circuit. Contact any service technician. If you wish to get some details; check the site linked here. Surf the site with patience. Pull up older posts.
http://electronicshelponline.blogspot.com/
It will be best to replace the power supply regulator board as card basis rather than making "Surgery" to it; which usually will make loss for both money and time. Even though you can make it right, it will cost around an amount equal to the cost of a new board; including the cost of (spare parts + service charge) More to say, most of the spare parts to it will be difficult to get from open electronic spare part market. This is true to most of the flat panel TV power supply boards; irrespective of its brand and screen size.

What you are describing is common in these sets. The power unit tends to cause the LED backlights to fail. It is a 50 dollar parts cost but you have to upgrade the firmware to prevent it from happening again

replace screen it's faulty period ensure it comes with T-con