Display won't turn on, is the panel dead ?

[MrVais]

Hey guys,

I've taken out my old ultrawide monitor from storage cause I had some free time and I wanted to finally end the saga.

 

Back then when it went off, I remember I was getting a new table top for my desk, and I turned off the display and unplugged the power cable from the display.

When I plugged the display back in the display won't turn on at all - but it does have the LED light on ( I assume it gets power ).

Tried the same power adapter and HDMI cable on a different monitor and everything works.

 

Today I took off the back panel to see if there's any board damage of some sort. To my surprise - nothing. (not that I can see).

I've attached some pictures if there's maybe some people with more knowledge than me. 

 

LG 29UM65

 

Any help will be appreciated,

Cheers. 

 

 

[MarvintheParrot]

My assumption is that the ports on the monitor are dead. 

 

But if someone else has a better answer, believe them.

[mariushm]

Get a flashlight and place it very close to the screen and see if there's some image / text / whatever ... if so, it means it's just the backlight faulty (one bad led in the strip of leds that light the panel at bottom and/or top could make the whole strip of leds not light up)

 

You can get a digital multimeter and measure the voltage going to the backlight.... you have those 33uF 100v capacitors at the top and the connector with one blue wire and lots of gray wires. One color is most likely the voltage and the other color the return (ground). 

There's a dc-dc converter circuit below those two capacitors which takes 12-18v or whatever from the power adapter and boosts it to whatever voltage the leds need, which you can measure across those capacitors, or on that connector. 

 

If you're curious, looking at the last picture you uploaded

 the chip by the power jack is some voltage converter to power the main big chip. 

The bigger chip above it with those 4 inductors (written 100 on them) is the audio amplifier for the speakers 

Above it on unpopulated area of circuit board I can only assume it's a copy of the backlight driver circuit , for panels that have more led strips or bigger panels. You can see the layout is the same, it's like copy paste but rotated. 

 

All the way top right corner is the backlight driver, which takes power from adapter and boosts it to probably 50-80v (let's say multiple groups of 12-24 x 3v..6v leds in series)

 

top left it's some voltage regulators for the actual lcd panel, most likely. 

 

 

 

[MrVais]

10 hours ago, mariushm said:

Get a flashlight and place it very close to the screen and see if there's some image / text / whatever ... if so, it means it's just the backlight faulty (one bad led in the strip of leds that light the panel at bottom and/or top could make the whole strip of leds not light up)

 

You can get a digital multimeter and measure the voltage going to the backlight.... you have those 33uF 100v capacitors at the top and the connector with one blue wire and lots of gray wires. One color is most likely the voltage and the other color the return (ground). 

There's a dc-dc converter circuit below those two capacitors which takes 12-18v or whatever from the power adapter and boosts it to whatever voltage the leds need, which you can measure across those capacitors, or on that connector. 

 

If you're curious, looking at the last picture you uploaded

 the chip by the power jack is some voltage converter to power the main big chip. 

The bigger chip above it with those 4 inductors (written 100 on them) is the audio amplifier for the speakers 

Above it on unpopulated area of circuit board I can only assume it's a copy of the backlight driver circuit , for panels that have more led strips or bigger panels. You can see the layout is the same, it's like copy paste but rotated. 

 

All the way top right corner is the backlight driver, which takes power from adapter and boosts it to probably 50-80v (let's say multiple groups of 12-24 x 3v..6v leds in series)

 

top left it's some voltage regulators for the actual lcd panel, most likely. 

 

 

 

Will take a closer look and try to figure it out now that I have much more info.

Thank you for this detailed answer.