Have sound but no picture.backlight LEDs flash once on/off 1st on.can see picture on screen (any channel) using flash light...already tried new LED converter...all working then screen went black.

I believe you have some shorted LED lamps on the backlight strips that are causing over current and shutting down the inverter protection circuitry.. New backlights should fix the set

What is the model number? If it is only 3 years old, I suspect you have a LCD TV with LED backlight. You quite possibly have a failed LED backlight.

Many LG TVs of this age are starting to fail due to over-worked LEDs in the backlight which create the white light that illuminates the LCD image.

The symptom is TV turns on and off ok, gets sound on the connected video inputs, but has an otherwise black screen with no video on display. You can try to operate the TV near a bright window with lots of sunlight and see if you can perceive a faint image on the screen. A flashlight is often not bright enough to be helpful.

Most of the time, an LED will fail as a short circuit and still allow power to flow through it to other LEDs that will still light up. If one of these LEDs fails as an "open circuit", or if several LEDs have failed in the same circuit, then the power supply detects a fault and shuts the TV down. If the LED is intermittent, you may have flickering. Think of having one light bulb burn out in a string of Christmas lights and having all the lights go out until the bad bulb is replaced... kind of the same thing.

Your TV circuits boards should be fine. In my opinion your TV requires a backlight repair which requires complete disassembly of the entire TV including disassembly of the panel which is a difficult process.

I saw a youtube video where they replaced the led strips and it fixed the intermittent flashing screen issue

Hi Terry,

If you can see the faint picture in flash light means the power supply and the main board is working. The real culprit is the backlight. Even one bad LED in the backlight will switch off the whole array. To repair this fault the panel has to be opened and the defective LED or LEDs are to be replaced.

This is a complicated, delicate and risky job and must be attempted by an expert only. You may end up damaging the screen permanently if you have not done it before and try to DIY.

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.

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

Best Regards!

Before backlight, I would always suspect TCON board