LG 55LN5710 - Have audio but backlights turn off

Hi guys,

My LG 55LN5710 TV has a strange issue. After turning it on, everything works great for about 10-15 minutes, but then the screen suddenly goes dark. I still have audio but no video. After some research, I did the flashlight test, and the image is indeed on the screen, its just the backlights that turn off for some reason.

After more research, the "likely" cause was a bad power supply/LED driver. Got a replacement part and did the swap. Unfortunately, the exact same thing happened, so now I'm back to zero.

The unfortunate thing is the TV is only 2 years old, and had only seen about 30 hours of use since we preferred a different room in the house. I'd moved my PS3 over to start streaming stuff to it about 2 days before this happened, so I'm pretty upset about this (it actually worked perfectly the day i hooked up the PS3, so no idea what went wrong).

Does anyone have any thoughts or ideas?


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The next video is very technical

And another model but the idea is the same. Only your better TV techs would know this area so you might have to shop around.


Too bad you didn't hear this before buying a power supply. Listen to him around the 20 to 30 second mark.

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Thanks for the response R. Proffitt!
However, I don't think I can use that solution.
here is a picture of the back of my TV (sorry, not sure how to embed the image):

Google Drive link

What I replaced was the big yellow/brown card in the middle.

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Amazing how Moore's Law keeps working.

OK, my video is more about finding a tech that has worked your model and found prior causes on same or similar models. I see there are only a few boards so use my friend's advice when we don't know which board to change.

"Replace the cheapest part first."

Some panels have the driver sections as part of the panel FRU and those are treacherous since you can have a failure there and go instantly to BER (as you are a TV tech I'll use tech acronyms.) When you go BER you often find the client is best kept in an area of non breakable or throwable items. Be sure you don't caffeinate them in advance.

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I admit I just did some pillow punching. Called LG just to try and troubleshoot. Got a pretty helpful guy. Told him i'd already tested different devices on different inputs, I'd done the flashlight test, etc. He suggested a factory reset, which I did. He then waited for me on the line for about 20 minutes and everything was working well. He said he'd created a report on the issue and had made a note in it about more thing to try before trying a repair. Literally a minute after we hung up it happened and I called again.

Got a different person. Told her what had happened. She suggested I try different devices and inputs. I told her I'd been through this with the guy and that he'd wanted to try something else, to which she responded the next step was a technician (pretty sure she was lying). To humor her, I asked about the cost. She thinks its either the main board or the actual panel. $195 for mainboard repair/replacement. $120 + cost of panel (which she didn't know) if it was the panel.

For now, I will try again tomorrow and see if I can find someone that will care enough to tell me what else to try.

Looking up the parts, the TCon Board is about $22, and the Main Board goes for $100-$120. So my options are:
1) Gamble and order the parts to see if any fix it
2) Get the LG repair
3) take it out back and kick it to death or smash it with a hammer

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Scratch 3)

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