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Backlight turns off after 1-2hours

My TV is a LG42LS570T

When screen goes black I can see the picture with a flashlight on the screen. And the audio is also fine.

When I shut down the TV for 5sec and back on - it can show picture again for maybe 1 hour or so. Sometimes the black screen comes ealier.

I have looked for errors on the PSU board and meassured all voltage 24, 12, 3.5V. And they are also there when the screen goes black.

I can't find the LED driver PCB in the Servicemanual, so not sure what to meassure on the output.

There seems to be some test points near the output connector and there the voltage vary from 5-24V (more or less) I guess its because of the actual brightness of the screen showing..

Since the picture is always shown I would think that the TCON pcb is ok..

Any advice will be much appreciated.

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@emek21 sounds like the actually LED backlight strips. Replacing those is a bit of a PITA but it will resolve your issues. Yes, your T-con board sounds ok as well as your power board. It should be very similar to this 42" LG TV LED Strip Replacement Tutorial Just take your time working on it.

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Last time I dealt with a backlight issue on a flat screen TV, I picked up one of those back light LED testers; best $20 I spent. Showed me exactly which strips were bad and verified that it was indeed the backlights that were the problem.

Easy to use, cheap and definitely worth getting.

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I was afraid of it could be the LED strips.

Do you know if I can test the LED’s without disassemble the tv completely? Just to be sure

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@dadibrokeit nice tester. But I would rather be able to test the strips without having to disassemble the to completely.

Not sure if that’s possible…

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@emek21, In addition to being able to test individual LED strips, the tester can also light up the entire display in place. Typically the backlight is divided in two sections, with half the screen being lit by each one of two power connections. So as long as you can get to those power connectors, you should be able to light up at least half the screen without completely disassembling it.

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