LG 75um6970pub tv turns on with a faint light.

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

Did you try repairing the PS with a repair kit first then replace both the boards after that?

The problem is defective LED back lights strips inside of the panel.

If you saw no faint picture with the flashlight, then it's the T-con board.

Hi Anonymous,
It looks to be a case of failed backlights.

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.

put jumper in between pin no 23 & 28 now your power supply is on but still no voltage at led out put error 6 code is particular for led out put not for t con so please replace power board complete

If the LCD panel back light is not lit you have a bad LCD panel. If the back light stays lit when the set is turned on then you almost certainly have a bad main board since you have already replaced the power supply and T-con.

I’m happy to help further over the phone at https://www.6ya.com/expert/dewayne_4a10eab6caecdb92

usually bad power supply, Where did you source your part? return/exchange it. Bad LEDs/ possible but not as likely, Tcon working if you can see images with flashlight. You must also have backlight on signal from main board ,check for 3 to 5v on labeled connecter on power supply. UPDATE---47" & 50" LN series. This model has had LED problems if your TV acts as described by Mr. Hughes in is answer to this problem you have bad LEDs

Can you see a faint picture when looking up close to the screen? If so this could be the screen inverter that lights up the screen that has gone!