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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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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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I have exact same symptoms and am wondering if you have since resolved the issue?

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I have the same exact tv with the same issue. I recently took it to a repair shop and they said it's either the driver board or led strip

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Reid Smith will be eternally grateful.
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