My LG 47LN5400-UA flatscreen has a black screen, everything works fine except black screen, when I shine flashlight on screen I can see full color picture, I have replaced the power supply/LED board.

Sounds like you have LED backlights that are going bad and the strips need replacing, its not a real easy job but if you watch some youtube vids they show how to do it.

replacing the led's is not so hard and could be a lot cheaper, you only need to replace the bad led not the whole strip, you can get them on ebay

The led driver AND the T-con board are bad. If you could see a picture with the flashlight then the T-con board would be good. It is not. The led driver can be on the main board or the power supply board. You can get these parts from here: TV Parts Universal TV Stands DLP Chips ShopJimmy

hi yes the led have shorted out thanks

shaun

It is your back light or the power to the back light that needs to be changed as to how much and how easy it is to change will depend on if you do it yourself or have a TV repair person do it.

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://electro-medical.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..

Contact LG Edward at 800 243 0000. Thank you and leave feedback

You need to replace the backlight.

Fault at its main digital board. Short circuited component/s at it. Contact any service technician; or the authorized service center. If you wish to get some details; check the site linked here. Surf the site with patience. Pull up older posts.
http://electro-medical.blogspot.com/
http://electronicshelponline.blogspot.com/
In most cases, the main board might have to be replaced. If so, a software [firmware] update too might be necessary.

Fault to the main power supply regulator section. Either it will be on a separate board, or on the part of its 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/