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TV powers on, LG logo and clock logo come on briefly, then no picture

LG 55LX6500 3D Model TV UB Build on the Main Board Images Below

A co-worker was just going to put this TV out on the curb, so I have no money in it currently. I have a science background but little electronics knowledge beyond basic computer hardware build skills.

I believe this model was new in 2010 or 2011 and has been sitting for a year. I'm trying to develop a trouble shooting plan.

The TV will power on with an audible click. On power, the power button on the lower right lights, and the button keys on the lower right cycle across (light up across then back), then the power light stays lit. No blinking or other odd behavior.

On power up, the screen briefly lights up with the LG logo and what looks like a clock icon, but with 4 dashes instead of a current time. Then the screen goes black.

I have the back cover off, and I have many small lights on the back that come on during power up when the screen has the LG logo, but go off after a second or two. Once the screen is black, I can press menu buttons on the front, and get a beep but nothing on the screen. The remote will power the TV on and off, and the menu button on the remote will make the button on the TV light up and beep.

I've seen the Youtube vid about baking the main board, but without knowing whether that is the culprit it seems risky to damage what might not be the broken part. Visually, I can't yet identify any capacitors that are obviously blown. I am considering giving the main board a short 5 min to 10 minute blow with a heat gun (carefully) to see if that might reconnect a bad solder joint but beyond that I'm not sure where to start. I don't want to buy and replace boards at random. I'm willing to spend a bit to get it back working for a gaming TV, but don't want to waste time/money. Any advice would be appreciated.

Back Panel Removed

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Main Board

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TCom /Middle Section

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Power Supply Board

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Hi,

As you are getting the logo I suggest that you try and see if you can reload the firmware into the TV. If you can't, you've only expended a bit more time, not money, on it at this stage.

Here is a link to the support page for your model. Scroll down to find the firmware install guide and firmware download links.

http://www.lg.com/us/support-product/lg-...

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Hi, thanks for the input. I thought about that as one of my first approaches, but I'd have to do it "blind". Thank you for the link. I'll see if I can step through the process as though the screen were working. Can't hurt as a noninvasive first step.

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Hi, I was kind of hoping that pressing the appropriate buttons on the remote would somehow give a picture as it may be hard coded in the TV firmware to enable the screen so as to perform the firmware update. Obviously a mistaken hope.

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Hi, that is what I was thinking as well, but I wasn't able to confirm that the update succeeded. I tried the approach of following the update instructions with the USB stick, and either hitting "enter", or toggling left (from cancel to enter if cancel was the default selection). I gave it a while for each try but neither time did the TV power off and back on as it should for the update process. Thank you for the suggestion though. It was a good first step.

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Confirmed this resolved my issue on my 55LA7400 as well as my black bar in the middle of the screen issue.

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Don, so your saying that doing the firmware update fixed the problem with the screen cutting out after a few seconds?

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Reid Smith, at this point do not consider any baking, cooking or other culinary adventures. The first thing you want to do is post some good pictures of your boards, "many small lights on the back that come on during power up when the screen has the LG logo, but go off after a second or two". You want to turn your TV on in a darkened room and produce an image on the screen (either a known working station or a video/DVD ) then shine a flashlight at an angle against the display. See if you can make out any silhouettes. That would indicate that your backlight is not working. Of course you can also use a multimeter and measure the voltages coming from your power board. Again, if you post some good images, we might find more information for you. The symptoms you are describing suit a failed backlight/inverter circuit.

Update (01/03/2017)

Let's see if we can get your backlight to come on. Try to force the power board ON.

SMPS TEST 1: To Force Power Supply On.

Disconnect P8000 on Main board.

(A) Jump pins 9, 10, 11 or 12 (3.5V) to pin 1.

Test Voltage Outputs 12V, 24V to Main and 24V to the Inverter.

Remove AC power. Leave the jumper in place.

SMPS TEST 2: (B) Jump pins 9, 10, 11 or 12(3.5V) to pin 18 (INV-ON). Apply AC power, the Backlights should turn on. Let me know what you have when you do this.

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Hi, thank you for responding. At the moment, I have the unit down in the unfinished basement of a condominium. In the interest of brevity (which I didn't really even accomplish) I left out of the original post that I gave the flashlight test a shot and couldn't see anything. I've done a little searching on the web in the last year to try to find information and potential resolutions but have only come across a few instances for this or closely related models. I've checked out ShopJimmy's YT video on the backlight/flashlight test and as best I can tell I don't see any silhouettes or faint images. Based on the ShopJimmy video, it look like my backlights come on briefly at startup (concurrent with the LG logo and clock symbol showing up on the screen) but then the backlights go off after just a few seconds.

I have a good multimeter. I'll stop by the condo later today and take some photos of the boards.

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Photos of the boards up. Thanks for any additional input. I can't see any latent image with the flashlight test. When the LG logo appears on the screen after startup (briefly) it look like a "full screen" image. In other words, it looks like there are no noticeable defects in the image that is onscreen with the logo. Uniform black background with the red LG logo. If there were backlight LEDs burnt out, I wonder if that would produce some noticeable effect on that startup image, even if it is only lit up for a couple of seconds.

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I doubt that it is the LED strips. you'd still get a picture, even so of different brightness etc. This does sound like a backlight issue until proven otherwise :-)

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Sorry, I just posted my question in the " answer column" ( I am new to this site).. I have same set with exact same symptoms, and am wondering if you managed to resolve the issue?

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My TV had the same issue. I would turn it on and the logo would flash and then the tv would go black. If you wait about two minutes the tv goes dark and then lights up again. After it lights back up you can click input on your remote and it will start working again. Or at least that is what worked for me.

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I have a LG 47 LX6500 had the exact same symptom. The TV worked & shut off properly but then this problem start at the next morning. I watched a few youtube videos pointed to one of LED light burned out and shorted so the LED power driver board detected voltage variation & shut off automatically. The burned LED must be replaced but there is too much work!

https://www.youtube.com/watch?v=hh3z_dkk...

https://www.youtube.com/watch?v=Bf5T2wwt...

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I have this same issue and ended up just using another tv and letting this one set its an lg 3d. Model 55LN4600 MANFUFACTURED 2012

In 2 separate occasions of letting it

Set for 4-5 months I would then rehook it up and it worked fine again both times for approx. a month straight perfectly both times then started the same cycle of coming on going black after 10 minutes.

Per the first time this happened before setting it aside for a few months it started the on lg to black screen cycle with a 10 min tv viewing time before going directly black then with 2 more weeks of having only 10 minutes of visual tv it then just came on and went right to black with sound and all other controls/options working as they should always of course.

My wonder is if it was an led do they recharge in some fashion after setting because once mine got to the point of going directly black after the lg screen to staying on and working perfectly for 1 month than to the 2 weeks on 10 min. veiwing to directly black.

Both times it was almost exactly the exact amount of time before the issues resurfaced.

My wonder is leaving it setting unplugged for those months just makes me think it is something other than led. When a bulb goes out it wouldn't work again would it.??

I'm not any bit knowledgable on these issues but wanted to see if any of you that are very knowledgeable and can put 2n2 together realized this has happened throughout my issue with the same problem as all have had above.

Sorry about the repetitive information. I wanted to be sure I was clear in my posting.

Thank u

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OK so it tried the push all the button on the remote not the channel one but as above the input and av mode etc. .

My TV has not went black yet again. .It went from to black in 10 minutes to being on for almost an hour and the picture isn't dim. I'll post as soon as it goes black ( not that I'm hoping for it to). It's also on the auto screen size per channel/show setting not sure if that changed anything.

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OK so it's been a few and my TV did go black again.BUT..this time after turning it on I caught the will turn of in 3 seconds message then it when black again.

I let play hence all else works,per the sound ect. And after 3 minutes pushed the energy saving mode on the remote and the screen came back on shafted it turned off my energy mode and I'm fine again so far. It's possible as another post I dug that it its just the economy setting mechanism the gentleman stated was a mandatory addition but my issue is it was only the screen that turned off. I think the switches are bad . But as it's stated it's stated have no idea how a TV works so it's stated going off of possibilities here and reading thru others postings.

I wanna,say thank u to all because U all helped me through my process of elimination of issues. Please focus on the energy settings.

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Reid Smith will be eternally grateful.
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