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LG 55UK6470 blank screen and no sound

Hi all,

I have been trying to fault find my broken LG 55UK6470. The screen went blank so can't get a picture out of it. There is also no sound.

I've opened up the back and tested the power board. I believe this to be working as the backlight LEDs turn on, and I'm reading 13v being sent to the main board on all the correct pins.

I ordered a new main board, thinking that this was at fault, and unfortunately this has not solved the problem.

I've tried to power it up without the Wi-Fi card attached, or the speakers attached encase one of those systems were at fault. Still nothing.

I'm assuming that the fault is with the display, and unfortunately I can't find any replacements for that.

Is there anything that you would recommend trying before I start looking at taking it to be recycled.

Thanks,

Simon

Edit: I have added pictures of the back of the TV, including voltage readings going to the main board.

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@craftyfox90226 Post some pictures of all tour boards with your question. You also want to measure all the voltages on the power board to main hoard connector. If it would be your panel

Than you should still get sound. For now we should assume your main board is okay. That leaves the power board as a prime suspect until

We get more info

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Thanks @oldturkey03 I have now added some pictures.

I have measured the voltages coming out of the power board and included these in one of the pictures. From what I can see everything seems to be putting out ok from the power board. There is power to the backlight LEDs and seemingly enough power to the correct pins on the main board.

Does this still put the power board as a suspect? It's the lack of sound that is really surprising.

Thanks,

Simon

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Hi all,

Thanks so much for the feedback!

When I was doing a bit of further investigation I came across this YouTube video that suggested to cover some of the ribbon cable in tape: https://www.youtube.com/watch?v=Xb756Qiv...

I have given it a go and its fixed the issue!!

What do you think could've caused this problem, and do you know of a more permanent solution to this? Change the ribbon cable maybe?

The sound is working too, I discovered that in trying to blindly reset the TV I had changed it to 'Optical out only', hence why the speakers weren't working!

Thank you again for your help!

Simon

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@craftyfox90226 the tape-off method points toward issues with the LCD driver boards. The only thing that a DIY'er can do, is exactly what you have done. The only permanent fix would be replacing the boards, which requires expensive special tools anda totally different skill set. I suggest you enjoy your TV since this method can last just as long as new boards.

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Sup mate. The problem could be the following reasons

# The power supply is broken

  1. The back light is broken
  2. Try connecting wired speakers and see if it makes any sound on startup
  3. The display panel might be broke

Hope this helps

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Thanks for your reply.

1, The back light is working fine, it goes on and off when it should, which leads me to thinking that the fault is somewhere else.

2, I've tested this by connecting my computer to the HDMI port and playing music. The computer picks up that it is connected to an LG TV, and that it is sending audio to the port, but there is no sound coming out of the speakers, or when I connect to the external white and red audio output sockets.

3, This is what I'm worried about as currently I can't see a way of repairing it. If it is the display that is the fault then it doesn't make much sense not having sound too.

Do you know if there is somewhere to buy a replacement display, or is it now destined for recycling?

Thanks,

Simon

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