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LG 47LN5750-UH - Only flashing LG logo upon plugin, resolved    
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jesch88



Joined: 20 Aug 2016
Posts: 3

PostPosted: Sat Aug 20, 2016 5:18 pm    Post subject: LG 47LN5750-UH - Only flashing LG logo upon plugin, resolved Reply with quote

LG 47" LED Smart TV
Model - 47LN5750-UH


I was given this TV to repair for someone. She says it was working fine then one day upon trying to turn it on with the remote, the screen just started flashing the LG logo and would not go to any actual input source. The TV is apparently out of warranty, but when she contacted LG customer service they said it might be an issue with the power supply, and could be as easy as replacing the power cord. Ordered a new one but it didn't cure anything.

This is a video of what happens upon plugging the TV in (without hitting power on either the remote or TV itself):

https://youtu.be/9Wy0VZZ6CTU

I'm decent with tech, but circuitry is kind of out of my wheelhouse. I researched similar issues on similar models, but didn't find any others exhibiting this exact symptom. Most resources said it was likely an issue with the capacitors on the power board going bad. I pulled the case off and visually inspected them. No bulging or visible damage on any of them.

Apparently, another possible culprit is the LED strip. I didn't want to go ripping even further into the case and ruining things entirely to check just yet. Hence, this post seeking help from those more capable.

Any insight would be incredibly appreciated. Would rather not tell her she needs to plop down another $500 on a new TV.

Thanks in advance.


Last edited by jesch88 on Sat Aug 20, 2016 8:20 pm; edited 1 time in total
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JTS1957



Joined: 21 Jan 2009
Posts: 2224
Location: Far, Far Away

PostPosted: Sat Aug 20, 2016 6:20 pm    Post subject: Reply with quote

Does the front LG (below the screen) behave the same whether LED back light connector is connected or not?
jesch88



Joined: 20 Aug 2016
Posts: 3

PostPosted: Sat Aug 20, 2016 6:37 pm    Post subject: Reply with quote

JTS1957 wrote:
Does the front LG (below the screen) behave the same whether LED back light connector is connected or not?


Honestly, I don't know because I'm not exactly sure how to test that. The behavior I know of is that the front light under the LG logo flashes red once each time the TV restarts after the logo on screen flashes then the screen goes black.



Opened the case back up. Could you tell me which connector is for the LED backlight so I can test it for you?
JTS1957



Joined: 21 Jan 2009
Posts: 2224
Location: Far, Far Away

PostPosted: Sat Aug 20, 2016 7:00 pm    Post subject: Reply with quote

Power supply board - Upper left. P801

Need to watch power indicator LED on apron.


Last edited by JTS1957 on Sat Aug 20, 2016 7:02 pm; edited 1 time in total
jesch88



Joined: 20 Aug 2016
Posts: 3

PostPosted: Sat Aug 20, 2016 7:00 pm    Post subject: Reply with quote

UPDATE: So, the problem seems to have resolved itself somehow. I powered on the tv without the case on and it immediately went to a "No Input" warning message. Popped in a Chromecast to test it and it's miraculously working.



But, that makes me wonder, could a case screw be causing a short or something on one of the boards to cause this? I don't want to reassemble the thing since it's "fixed" only to find it's messed up again.
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JTS1957



Joined: 21 Jan 2009
Posts: 2224
Location: Far, Far Away

PostPosted: Sat Aug 20, 2016 7:03 pm    Post subject: Reply with quote

Just be sure to replace screws into their original locations.
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