LG 22EA53VQ-P "crash" after 5 min.

[Zariel]

The monitor is perfectly fine for 5 minutes and after that shows flickering, see the video.
I checked the powersupply, the voltage is ok.

All i hear is a pitch noise coming from one of the components in the pcb.

Anyone has ideas?

https://youtu.be/aiPf4Ot2J48

[momaka]

What happens if you power off the monitor and immediately power it on again? Does it flicker ("crash") right away or does it take another 5 minutes? If it flickers right away, the problem may have something to do with bad solder joints or a marginal component that goes bad once hot. In which case, you can start narrowing the problem down by inspecting all solder joints on the main board. I don't see any very large components that could have bad solder joints, but it might be worth to resolder some of the bigger components (like the inductors).

Let us know what you find, though.

The flicker could also be due to a bad backlight, but we will investigate that, if needed, only after you address the above questions.

[Zariel]

Dear momaka!

Thankyou for your reply.
No, it takes another 5 mintues to flicker again when powered down/up.

[momaka]

Hmmm. That almost seems like a firmware bug then, especially if the problem takes exactly the same time to show up.

Looking at the video again, it appears the back light is fine and rather only the picture is doing it. Slim chance this could be the problem, but have you tried the monitor on a different PC just in case?

[Zariel]

Yes with pc and without pc too, its exactly the same and the timing is too.

But, when turned on after 2-3min it does a little flicker for 1-2 secs, and a pitch noise comes from the monitor then the picture is perfect again, and after 2-3 min again the monitor goes like in the video.

Seems like one component is failing while in duty but i dont know which one.

Edit:

Maybe the buzzing noise comes from this component only when the monitor goes bad:

[momaka]

Interesting. That appears to be the T-con's AVDD inverter coil/inductor.

So could be one of the two things: either the T-con board's power is being cycled On and Off, thus causing the noise *or* there is a shorted or partially-shorted ceramic cap on the t-con board that pulls down one of the power rails, and that causes the power to the monitor to cycle continuously.

To narrow it down, let's try the following:
Disconnect the flat LVDS ribbon cable going to the t-con - the one shown on the left in this picture.
https://www.badcaps.net/forum/attach...4&d=1513941077
When you do this, there will be no picture on the monitor (it's OK for the screen to turn fully or partially white... or even black in some rare instances)
Then, turn On the monitor while connected to a running PC. Make sure the PC is not set to go to sleep or turn Off the monitor so that it can run much longer than 5 minutes (or however long it takes for the monitor to start flickering).
Now see if the monitor starts flickering again. If it does, then the issue must be somewhere on the logic/video board and/or power supply. If NOT, then the issue is likely on the t-con board. We will pickup from there, once you let us know which one it is.

[Zariel]

Okay, i done what you said step by step.

The following happens: There is no buzzing sound so yes the t-con board is disconnected and the screen is turned on fully black.
There is no flicker at all, perfectly fine black screen without any noise.

[momaka]

Ok, for the next step you will need a multimeter with resistance measurement setting. If it's a manual-ranging multimeter, set it to the lowest resistance scale (typically 200 Ohms) and measure the resistance between ground and each of the following test points:
5V
VDD
VGH
VGL

I see a few more test points, but your pictures are a bit blurry, so I can't tell what names they have and if we should measure those too (you may want to upload a better picture of the T-con, if possible). By the way, do the resistance measurements with the power OFF and the monitor disconnected from the wall.

In addition to the resistor measurements, also perform a voltage measurement for the above test points I listed with respect to ground (i.e. any metal part on the case of the monitor). Do the measurements when the monitor is cold / still works and then after it crashes too, so we can compare.

Then post what results you get here.

[Zariel]

Hi sorry for the very late reply, had life changing events.
Today i found the box with the monitor again. haha.

The inductor burned out, smoked so i had to get it out.
Now i only get a blank black screen so backlight on, no smoke, no heat.
Maybe theres a short somewhere, i dont really know.

I did the measurements (years later haha, sorry) you asked.



5V
voltage: 5.27v
resistance: 0.74 ohm (multimeter set to 20k ohm)

3.3V
voltage: 3.49v
resistance: 1.01 ohm (multimeter set to 20k ohm)

VDD
voltage: 0v
resistance: 3.89 ohm (multimeter set to 20k ohm)

VGH
voltage: 0.06v
resistance: 47.4 ohm (multimeter set to 200k ohm)

VGL
voltage: 0.29v
resistance: 6.10 ohm (multimeter set to 20k ohm)

[momaka]

Originally Posted by Zariel

Hi sorry for the very late reply, had life changing events.

No problems!
Hope they were all positive.

Originally Posted by Zariel

Today i found the box with the monitor again. haha.

The inductor burned out, smoked so i had to get it out.
Now i only get a blank black screen so backlight on, no smoke, no heat.
Maybe theres a short somewhere, i dont really know.

Yeah, that inductor is likely part of the first boosted voltage rail for the T-con, typically referred to as VDD or AVDD. Might be a shorted SMD ceramic capacitor, or it might be the panel going bad.

Originally Posted by Zariel

I did the measurements (years later haha, sorry) you asked.

5V
voltage: 5.27v
resistance: 0.74 ohm (multimeter set to 20k ohm)

3.3V
voltage: 3.49v
resistance: 1.01 ohm (multimeter set to 20k ohm)

VDD
voltage: 0v
resistance: 3.89 ohm (multimeter set to 20k ohm)

VGH
voltage: 0.06v
resistance: 47.4 ohm (multimeter set to 200k ohm)

VGL
voltage: 0.29v
resistance: 6.10 ohm (multimeter set to 20k ohm)

Yup, looks like VDD, VHG, or VGL is shorted and pulling the rest with it... though I suspect VDD is the likely rail with issues.

Now the resistance you measured... does your multimeter have just a 200 Ohm scale and NOT 20k or 200k? If yes, use the 200 Ohm scale and take the resistances again.

I suspect something like ceramic caps C110 or C112 or other similarly-sized caps might be bad, causing this issue. But when you post the resistances, then we might be able to get a better clue. That said, can you post more and higher-resolution / better quality pictures of the T-con board so that I can try to trace the circuits out?

[Zariel]

Dear Momaka!

I will post everything you asked when i get home, wednesday!

I have a Manual multi meter, i have a picture of it: http://imgur.com/gallery/kDfMAjT

Yes i had no clue about how the resistance mode worked on my multimeter, but now I do.
Will test in 200ohm next time when I'm going to post.
Also i bought a Caterpillar S60 since then so i could use a thermal camera too, finding possible shorted components.

Again, thankyou very much for your efforts and caring about my learning process.

[Zariel]

Hello again!

Sorry for being late.

The pictures you asked, i hope they are enough high resolution: https://imgur.com/a/Sulvpgt

Also, i couldnt measure the resistances with my multimeter set to 200Ω, i had to go switch to higher range so i could only take the same measurements again, with the same results, 200Ω would not read anything for me. (out of range?)

I suspect Capacitors: C125, C126 are burned out, checked them respect to ground and only one leg of C126 are beeping, C125 none of its legs are beeping, also checked their 2 legs and no beep, no values, they burned out so they are open circuit now?

The cap under them to the right a bit, with similar size checks out good in diode test mode with my multimeter: one leg beeps, another leg shows value of 1302.

Other caps are doing well and as intended compared to these two caps it seems.

This could be the problem?

Thankyou.

[momaka]

Could you please upload your pictures on badcaps.net forums?

For some reason, I get a blank screen when I follow the imgur links, so I can't see any of the images.

[Zariel]

Sorry I couldnt upload photos from my Android Xiaomi Note 8T with chrome browser in time, now im at my computer, will do.

I couldnt upload the original images ( they are 10376KB-13585KB each )

Google drive so u can see original images:

https://drive.google.com/drive/folde...Z9?usp=sharing


Also i will attach the compressed images:
Virustotal:
https://www.virustotal.com/gui/file/...10f80d65875c7f

[momaka]

Originally Posted by Zariel

I couldnt upload the original images ( they are 10376KB-13585KB each )

Yeah, that, and the forum has limit for standalone images set to 3000x3000 pixels max (which is actually adequate if you resize your images.)

Anyways... no problems either way, I just got the images from the attachment.

Originally Posted by Zariel

Also, i couldnt measure the resistances with my multimeter set to 200Ω, i had to go switch to higher range so i could only take the same measurements again, with the same results, 200Ω would not read anything for me. (out of range?)

Yes, if you get no reading on the 200-Ohm scale (only a "1" on the left side of the display or an "OL".)

Originally Posted by Zariel

I suspect Capacitors: C125, C126 are burned out, checked them respect to ground and only one leg of C126 are beeping, C125 none of its legs are beeping, also checked their 2 legs and no beep, no values, they burned out so they are open circuit now?

No, not necessarily.

Ceramic capacitors typically go short-circuit / low resistance when they are -bad-. Typically low resistance for them is under 30 Ohms (though, they can sometimes become partially shorted and read around 100 Ohms... but it's rare.) That being said, the resistance measurement won't tell you if those caps are good. It can only show you if they are bad.

Looking at how they are connected:
C126 has its lower pad connected to ground, so it's normal you get a low resistance / short-circuit / 0 Ohms to ground. Its upper pad appears to be connect to upper pad of R126 and also possibly the lower pads of C125 & R125. Meanwhile, upper pad of C125 is connected to test point VGH. So for these two ceramic caps, just check if you read any low resistance across them, rather than measuring to ground. While at it, also check R125 resistance. I can't make out what value it should have from the picture, but it appears as either "561" (560 Ohms) or something "-R5", suggesting x.5 Ohms.
Check diode D2 (with diode test on multimeter) as well. It should be a dual diode. Unsure of internal connection/orientation of the diodes, but it should become obvious from the measurement and you shouldn't get a short-circuit between any of its 3 pins.

Originally Posted by Zariel

The cap under them to the right a bit, with similar size checks out good in diode test mode with my multimeter: one leg beeps, another leg shows value of 1302.

Well, we can't necessarily say if that cap is "good", but as it's reading that high on diode test mode means that at least it's not shorted... so we can give it a pass for now.

Originally Posted by Zariel

This could be the problem?

Well, let's start back from the beginning again, since nothing appears obviously bad... but this time with a little more detail.

First, check fuse F1 (see 1st or 2nd image for reference) - it should show a good low resistance on the 200-Ohm setting on your multimeter (1-2 Ohms max, depending on how low your DMM can measure.)
- If F1 is bad only, check resistance (200-Ohm... or if not, then 2000-Ohm scale) between pad labeled "5V" and ground and report back what you get. Otherwise continue below.

Go over to where inductor L1 is. I see that you removed it... which is actually helpful here. For this one, measure resistance (again, 200-Ohm scale first) between test point labeled "SW_VDD" and ground. Report back what resistance you get.
If it's reading low (less than 100-200 Ohms, approximately), either diode D1 might be bad -OR- chip UC2 might be bad (or both). To check further on this one, remove diode D1 and check again. If low resistance is persistent with D1 removed, then UC2 might be bad.

While at it, again check the resistance between test point "VDD" and ground (on 200 or 2000-Ohm setting again.) Report back what you get.

And that will be all for now.