LG TV was displaying a white screen. I replaced the motherboard and not getting any video on screen. Is it repairable?

The power supply is bad or problems with the screen or with the the LCD.

It sounds like you may have an issue with the backlight of your TV. If a backlight is not getting adequate power, it can cause the screen to appear blue or have "flashing white splotches". The best way to resolve this issue is to have a qualified technician inspect the TV to determine if there are any issues with the backlight power supply. If there is an issue with the power supply, they will be able to replace it and resolve the issue.

That is usually a sign that the power supply or the LED's in the display are failing. You may be able to order new power supply or parts for it from shopjimmy.com

That is the right amount of voltage the issue is when one or more of the individual LED lights fail, the current changes and the power supply senses it and shuts down.

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.

Sounds like a backlight problem to me. If you input a signal to the HDMI or Composite input and then it goes black have you tried taking a flashlight to the screen to see if the picture is still there but just dark? That would indicate a backlight issue. That model appears to be an LED edge lit backlight, so if the picture is still there after going black your going to have to trace out the backlight circuit and see whats going on. Usually with LED backlighting if it comes on at all then the LED's are good, its just the driver supply thats failing to keep them on. Some TV's have a small separate board that provides the backlight control, but i suspect with this model its on the power supply board and not the motherboard. Have you checked that board? It could be bad caps on the power supply board, check the voltages to the backlighting when it lights up and then when it goes dark. It could just be some failed capacitors on the power supply causing that voltage rail to drop off.

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.

Sounds like the backlight has failed.

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