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LG TV Random LED Backlight Failure, Power Supply or Faulty LED?

Hi all,

I am currently at a stand still with an issue. My LG TV (70LB656V) will work power on and function fine, however, as soon as a movie, video or TV starts to play, the LED backlights will power off after a random amount of time.

Troubleshooting:

I have managed to extend the time by turning power saving onto maximum and turning the brightness down to 50%.

Power supply board (EAY63072301) has a red LED light on, which appears to flash a fault code of 4.

Voltages to LEDs seem normal until failure occurs.

There is 120v from the heatsinks on the MOSFETs to ground (Is this normal?).

Question:

I would like a second opinion before i go ahead and purchase one, but does the issue occuring sound like Power fault, or LED fault? And does anyone happen to know the meaning of the fault code on the power supply board?

Thanks.

Update (09/18/2019)

@oldturkey03 The LCD still worked fine. I believe I located the issue. A bit more prodding around and I found that there is a LED that is not working, which if I understand correctly, it actually causes the entire array to slowly malfunction over time.

Will replace the LED and respond with the outcome.

Update (09/28/2019)

Turned out there was a blown LED, I have replaced the LED that had blown and it is working 100% again.

Contestado! Ver respuesta Yo también tengo este problema

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@kiwitronics that is correct. that is where i was going with those tests. LG has had issues with their backlight arrays. Those are a bit of a PITA to replace since you have to pull the panel apart. The larger the panel the bigger the chance of failure :-)

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@oldturkey03 yeah mate, I had it apart a couple days ago to mount all the defuses back into place, just purchased it faulty (all the defuses had failed out of place) put it back togeather, worked mint for half a movie and backlights went off. I was trying to avoid having to pull it back apart again but glad I did.

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@kiwitronics should have told us that you have had it apart already :-) that way we could have gone straight for the LED's :-)) Best of luck to you.

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Am having same issue, am in Sharjah , any hope to fix it?

LG told to replace it which I cost to buy a new TV

prasanth6410@gmail.com

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@kiwitronics once the backlight has failed shine a flashlight beam at an angle against the screen. see if you can make out the screen that way. If so you know that it is your backlight that has failed. Then you need to give us the voltages for the backlight LED while the backlight is working and what it is when they are not. If the dimming of the backlight helped to make it last longer it is a greater chance that it might be the power supply.

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@oldturkey03 So I have the exact same issue. The tv model is a LG 70LB6560, with the exact same power supply board and main board numbers as mentioned above. I have already replaced all the backlight led strips after the backlights started turning off. Worked again for about 1 week and then picture starting turning off randomly again. Flashlight test shows a picture and there is sound. I have voltages on backlight led terminals when backlight on but when picture goes black all LED+, VC_1-16 go down to 0. The red led on the power supply board flashes 4x also and it starts flashing around 10 seconds before backlights stop working.

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@Troy Barrett have you replaced any of the boards? My concern here is that this could be bad backlight strips or a bad power board/main board which may turn the lights off. Check the voltage on the BL on pin on the main board and see if it stays on.

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@oldturkey03 No I have not replaced any cards just all the backlight strips.

Not sure where I'm checking voltages for BL on the main board sorry?

If I unplug the 24 pin plug from main board to the PSU then the whole tv turns off completely. I'm assuming I have misunderstood what is meant here.

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@Troy Barrett you are right. Scratch that about the BL turning on. I'll edit that comment. I should have the schematic for this TV so bear with me until I get time to check it later on.

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@oldturkey03 as per the photos I checked all 3.5v,12v and 24v terminals while backlights were out, all voltages were as per the service manual voltage screenshot.

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My tv is LG 55LB671V. After some time ago my tv started turning off in a random time…. I opened the back cover of my tv and the LD701 LED was blinking 3 times every some seconds… I thought that maybe was the power board, but i also red that if the LED on the power board blinks for 3 times that means that i have an open LED strip. Also when the problem starts i have slound qnd i have not video but when i go closely to the tv on the up left corner i can see the video on my screen with my screen brightness to be very weak. Furthermore, when the problem occurs, i close and i open the tv and the screen is perfect with no problems after the next time. Some times my tv before shut down the screen it creates darck areas on my tv (you can see the screen behind but it is darker than other areas) and eventually my video wi turn off (with the sound to be okay) until i reopen it.

So is it is bad strip problem and i have to replace it? Or is it a but connection on yhe strip and i can fix it without any parts.

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Can I chip in here with a related question? Very similar fault on an LG 55LB700V

Screen goes black after a few seconds, Took the back off and found that the PSU (EAX65424001) is flashing error code 4.

Does anyone know the PSU error codes?

If I unplug either of the two LED plugs, I get code 3, which I think someone said was OC on the LED string. Makes sense. Before the screen blanks out, I see that it’s evenly lit, so SUSPECT that the LEDs are fine and it’s jsut the PSU, but wanted to be sure before I push the button on a refurb board from eBay.

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f I unplug either of the two LED plugs, I get code 3, which I think someone said was OC on the LED string. Makes sense. Before the screen blanks out, I see that it’s evenly lit, so SUSPECT that the LEDs are fine and it’s jsut the PSU, but wanted to be sure before I push the button on a refurb board from eBay."

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i have the same symptoms (although the 12v dc rail is down to 11.70v is to low?

was wondering if you replaced the PS board? did it fix it?

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I replaced my psu board ($80) from Ebay, tv worked perfectly for 2 weeks, but now it`s back to the same...

turns on for a few seconds then blacks out....hhhhmmm

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Richard Gormley that sounds like bad backlight strips. I‘d replace those since it is unlikely it is your power board again.

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