LG 4K Widescreen - stays black after initial power on

BerryTogart

Bolt Thrower.,
Long shot but perhaps someone has an idea.
I have a LG 4K screen here that was bought some time ago on amazon and which I received with the problems I'll state below.
Amazon did send a replacement and never did want the damaged screen back in the first place.

I can just dispose it, but then again I figured why not check if something went loose thats easy to fix. So perhaps anyone with more technical knowledge can give me an idea, I didn't see anything obvious.

The screen turns on, shows an image for a short time (as well as the OSD), then goes black. Pushing the power button again has no visible effect, bringing up the OSD doesn't work - the power still seems to be ok though as the indicator for power is still on.

Googling netted the idea, that it could be the capacitors, when checking the boards (see below) I didn't recognize anything out of the ordinary however.

Does anyone have a clue what I could check to get the thing working again or can confirm after the error behavior that this is some issue that needs expert fixing? (I managed to build a consolized neo-geo that doesn't win any form of beauty contest but works, that should give you a general idea of my own skills)

signal-2021-01-23-191309_001.jpeg
signal-2021-01-23-191309_002.jpeg
signal-2021-01-23-191309_003.jpeg
signal-2021-01-23-191309_004.jpeg
 
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DaisyAge

B. Jenet's Firstmate
I'd start looking at the display driver board, usually the one with the ribbon cable to the screen and start checking the caps there. Also look for a service manual, it may show you the values and voltages that are supposed to be going to that board so you can check them against your multimeter.
I don't suspect the power caps since it does turn on and the indicator never goes out, but it could be a faulty voltage regulator or transformer that's not outputting enough power when the screen starts drawing power.
 

awbacon

Jaguar Ninja
and the screen is BLACK BLACK right? Check in the absolute dark...it could be the backlight is off but the screen is on. Doubtful but...

I fixed a friends TV that had the exact issue. A Samsung. It was bad caps on the driver board.
 

NeoTeam546

Kuroko's Training Dummy
and the screen is BLACK BLACK right? Check in the absolute dark...it could be the backlight is off but the screen is on. Doubtful but...

I fixed a friends TV that had the exact issue. A Samsung. It was bad caps on the driver board.

This, turn the screen on make sure it has a picture you recognize the graphics/placement then shine a bright flashlight on it to see if the image is still there when the screen is black. Had a couple older TV's go out and they needed new inverter boards (often the whole PSU and inverter is on a single board now so you have to replace the whole thing if you dont have the tech skills to troubleshoot individual parts). The one board had visibly bad bulging caps.
 

awbacon

Jaguar Ninja
This, turn the screen on make sure it has a picture you recognize the graphics/placement then shine a bright flashlight on it to see if the image is still there when the screen is black. Had a couple older TV's go out and they needed new inverter boards (often the whole PSU and inverter is on a single board now so you have to replace the whole thing if you dont have the tech skills to troubleshoot individual parts). The one board had visibly bad bulging caps.

Good Sir my post count clearly indicates that Al Bundy is MY avatar...make yours Jefferson or something!
 

NeoTeam546

Kuroko's Training Dummy
Good Sir my post count clearly indicates that Al Bundy is MY avatar...make yours Jefferson or something!

Oh wow great intimidation in a troubleshooting thread. :lol:

Write to a mod to have them ban my account if it bothers you that much.
 

BerryTogart

Bolt Thrower.,
I greatly appreciate the technical support as well as the additional free drama that is created in ng.com style. Thank you :)
 
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