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Repair guides and support for your LG TV.

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LG49UF6490's Logo shows but no picture and no sound

I have a 49inch LG TV (LG49UF6450).

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I’ve tried measuring the motherboard’s voltages (listed as Drver ON, GND, 13.2, 13.2, GND, and Power ON and they seem to be fine (as shown below).

  • 3.49V
  • GND
  • 13.16V
  • 13.16V
  • GND
  • 3.39V

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Then I was doing more research and it was told somewhere in this forum to heat up the motherboard to 180C for 10 min and then back to room temp to see if that will affect the cold solder joints of the BGA (possibly) and it didnt work. I put it in a thermal chamber at work to try it out.

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I’m not really sure what else to do. It’s not as easy to measure most voltages within the connector because the hole is too tight but I measured around some caps and they dont seem to be shorted.

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Does anyone have any other suggestions other than heating up the motherboard? Am I missing anywhere to check for shorts?

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Update (08/15/2019)

@jayeff I did download whatever was listed in the 49UF6490 section even though the 90 model isn’t listed in the reference list.

It’s a little difficult since I went through the PDF to how to get the software into the USB drive. The problem is that

  1. I plug in the USB stick with only the software in it
  2. As I turn on the tv, the USB stick flashes for a sec and then turns off, as if the TV tried to read the USB but didn’t have enough power to leave the USB on for the firmware.
  3. formatted the USB to FAT and FAT32 and tried it again, and they didn’t work (acted like #2)
  4. formatted different USBs to FAT and FAT32 and they also acted like #2.

I’m going to give LG a call right now since they are open until midnight CST. Maybe they will help but I got this TV as a gift and I dont know if they will help since it’s a 2015 model.

Update #2

They told me version 03.15.86 is for my TV, so that is ok.

I need to talk to a Level 2 department, but they are closed. The person on the phone didn’t know the answer to my USB problem, so I’ll call them tomorrow as to why my USB cannot keep itself on while plugged in. It may be a firmware version issue or maybe I need to format my USB to something else other than FAT32 or FAT.

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Hi @antronna ,

It may be a firmware problem since you say that the logo is coming up OK.

Try updating the firmware for the TV and check if this resolves the problem.

Here’s a link to the firmware support page.

Type 49UF6400 into the search box and then select the “49UF6400.AUS” option that appears below.

When you are on the 49UF6400.AUS software update page, select the Reference link on the right side, middle of the page and then verify that your exact model number is listed.

If your exact model is not listed in the reference list DO NOT do this as you will brick the TV!

If it is listed, download the TV software update guide .pdf file as well as the Software File (version 03.15.86).zip file to your computer. Use the guide to find out how to update the TV using a USB flashdrive.

It will not install if the software in the TV is the same version as what the downloaded file is, but given that the file is dated 06/14/2019 hopefully the TV won’t be updated to this version already.

UPDATE:

I went back over the link I posted and realized that your model - 49UF6450 is not listed in the compatible models list only the 55UF6450 and 65UF6450 versions. It does mention a 49UF6430-UB - is this your model by any chance?

I couldn’t find your your particular model in the LG support pages. Try searching from where you are and see if you can find it. Search for LG49UF6450 support (or perhaps LG49UF6400 support- that’s how I found what I thought was it).

Unless you can find the correct firmware for your EXACT model or can confirm with LG that this may be the correct one, don’t try it

Sorry for misleading you.

Update (08/15/2019)

Hi @antronna

You may have to contact LG to confirm or refute re the firmware.

You’ll notice on this link that it says “49UF6490.AUS software update” but then goes on to say SW File(Version 03.15.86) for **UF6400-UA, **UF6430-UB, **UF6450-UB and doesn’t mention the UF6490 models at all not even in the Reference list.

Still can’t find it anywhere else

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@jayeff Ah Interesting. I'll try that after work. Never thought of a firmware problem. I'll keep you updated. Thank you for the response!

さんによる

@jayeff the -UB version is my model. Whoops I realized it's the LG49UF6490-UB not 50..I'll be looking around this website for the firmware

さんによる

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最も参考になった回答

@antronna since you said that your “Logo shows but no picture and no sound” it will not be your backlight. The Logo gets illuminated by the backlight so if it shows your backlight is okay. I am not a friend of just going to go ahead and reheat just any IC. Sure, a reflow might work but in the case of your TV you’d have a couple of IC’s that could be at fault. At this point I would suggest you get a replacement main board. That is where the Firmware sits, the USB circuitry etc. is on this board as well. Try to get either a known-well used one or get one from a place that has good return policies just in case a new main board will not work. Going by your pictures your main board is a EAX66703203

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@antronna Does your TV show the logo for ~1 sec before the screen goes blank then shows nothing? I’ve repaired that issue on an a similar model because the LED back lights were going bad. The back light would pull too many amps and auto-shut off the unit, even though they all still technically worked. When I took the TV apart, I found a small brown ring around all the LED’s.

It was a really strange issue, but I was able to fix it successfully on two separate units. Here is a link to the parts I would use to fix this. Since you have a strange model of this LG TV, I would recommend you take the TV apart and record the model number off the LED strips before ordering. This will ensure you’re getting the right ones.

Best of luck with your repair!

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Beeta Z さん、ありがとうございました!
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