Chosen Solution
Hi, my TV model is LG 42LA620V, it’s a smart TV, the screen went black while we were watching programs, but we can still hear the sound, and also can see something moving when the room is dark, and I tried to turn it off, unplugged all cables, and when turn it on again, the power light goes off, the logo showed on screen for a second, then the screen goes black again . I called LG, they said it seems like the backlights gone, need a replacement, but after replacing backlight, nothing changed, so really don’t know what to do. Anyone knows about this problem, please help me? Thanks a lot. Update (09/26/2018) Pictures as follows :
Maggie Tang this”also can see something moving when the room is dark “ is a backlight issue. You said you replaced the backlight but did not tell us exactly what you replaced and if it made any difference at all. If you replaced the LED backlight array, then I would check the power board and the main board. Keep in mind that it is the main board that tells the power board to turn on the backlight. So, measure the voltages on the power board for the LED’s and let us know what you get. Careful, some of those carry pretty good voltages. You do want to post some images of your boards with your question so that we can see what you see. Use this guide Adding images to an existing question for that. Update (09/29/2018) Maggie Tang no obvious damage on the boards. You will have to get a multimeter out and do some measuring. On connector P801 measure the voltages going to the LED backlight. Expect to find between 70V and 105V. Those are VDC so set your meter on the AC scale. Black probe to - (neg) and red probe to + (positive) With the TV turned on (careful so you don’t get zapped!) test the voltage. Let us know what it is. If you do not get that voltage then the issue is most likely your mainboard, but you do need to check the voltages on P201 as well. The voltages expected are printed on your board. Let us know what you find.
