Problem switching on LG TV, red LED flashes 3 times

[ayecrut]

Hi everyone,

I have picked up an LG brand television, manufactured in 2014. The model is LG-49UB850V / LG-49UB850V ZD (Link).

When I tried to start it the first time it didn't work, the screen remained black and the red LED blinked 3 times or just stayed on all the time. After moving it and plugging it in somewhere else, it restarted once or twice, but since then it hasn't started with the same symptoms.

Other information:
- The physical button that turns on the TV without the remote doesn't seem to work. Nothing happens when you press it, we can only interect with the remote control.
- On the PSU, when an attempt is made to switch on, LD701 flashes 5 times (orange) after about 30 seconds
- On the MB the red LED always seems to be on

Electronic card references :

PSU : EAX65613901
MB: EAX65684604 (1.0)


What can I do to find out what's causing the fault? Do you have any equipment you can recommend to check the condition of the welds? I have a magnifying glass, but it's not very practical.

I also have access to a multimeter but I'm not sure where and how to check the voltages.

Thank you in advance for your answers

[nomoresonys]

Seems like a mainboard issue.

[ayecrut]

So does the part have to be completely replaced or can it be repaired? Do you have any recommendations?

[nomoresonys]

Well troubleshooting and fixing mainboards can be very tricky for even the most seasoned pros, if a replacement board can be found at a reasonable price, that would probably be the way to go.

[nomoresonys]

Since there can be different boards for same model tvs, you want to match up the digits of the sticker on the board, which will indicate the correct part number.

[ayecrut]

Thanks, i will look into that