LG OLED77B29LA shuts itself down/doesn't start

[ILoveZeroTwo]

Hello,

I'm trying to fix a TV that got damaged by rain (open window during a storm).

The TV at first would start up and work completely normal, with no lines on the screen or anything. But after about 30 seconds, it turned itself off. After it shut itself down, starting it up directly afterward is no longer possible.

The standby light is red and it blinks once on the power-on command by the remote. The relay also does not click anymore when plugged into the wall.

Standby voltages are all present and stable, approximately 13V for the 20V line and approximately 8V for the 12V line. For 2 seconds after pressing the power-on button, the voltages hold their rated values (12V and 20V) but go straight back to standby.

It turns on again for somewhere between 3-30 seconds after waiting roughly 24 hours. The longer the wait time, the longer it seems to stay on.

I tested the PSU (3.5V to PWR_ON, 12VT_ON, and DRV_ON) while connected to the TCON and not connected to the mainboard. All voltages were present and stable (12V, 20V to the mainboard, and 12V + 23V to TCON for 10+ minutes).

On another try, I removed the lower LVDS cable between TCON and the motherboard, with everything else connected, to stop the SOS signal. The relay clicked and the TV started (USB started lighting), but after 30 seconds the relay closed again (no USB light).

Then I removed the heatsink from the mainboard to check if there were shorts on capacitors or oxidation from the rain, but everything seemed fine. Only the step-down output has a quite low resistance path of 24 ohms to ground, but I don't know whether this is fine or not.

I also checked all connectors, and they look good.

I would be glad for any help.

[Diah]

don't do any things... put it under sunshine days long till the wet went out from cells

[EazyBone]

If this got wet, chances are it made it down to the ribbons on the bottom.

It's not the boards you got to worry about it's the panel.

I would get a fan and try and put it towards the bottom of the TV not super close to move the water but just to help evaporate it, if there is any openings (usually sealed well) and try and see if any residual water may be in there will evaporate. Id leave it for couple days then try it again. Put the boards on also so they dry out also.

Then I would try again.

Edit

Looks like diah has same idea.. maybe that's better actually so it doesn't move water into places you don't want it.

[nomoresonys]

To be safe I think I would give it at least a week to dry out.

[ILoveZeroTwo]

Ok, thanks everyone for the recommendation. I will let it stay for a week and hope for the best.

[Davi.p]

Hi, how much hot is the temperature there in this time? If it's very hot maybe all tv parts are already dry, this is revealed by the tv fully working for few.. my bet is that one part of a board is severely oxidated, the place where dirt water better stays for long is under the BGA chips.. the most important thing to do is to make a fast self test of the couple PSB+screen, it is already described how to in the other threads, if you come down to a bad main board, well you decide what to do if buy another one or try to fix it, there is a simple fix for it but i can't describe it sorry..
further tips to test it, locate the bad chip by freezing it with duster spray can, the freezed chip that permits tv to boot or work for longer is the defective one and you can also let to reball it from a repair center.. also the bad chip would get abnormally hot when tv is running "well"..

[ILoveZeroTwo]

Hi, how much hot is the temperature there in this time? If it's very hot maybe all tv parts are already dry, this is revealed by the tv fully working for few.. my bet is that one part of a board is severely oxidated, the place where dirt water better stays for long is under the BGA chips.. the most important thing to do is to make a fast self test of the couple PSB+screen, it is already described how to in the other threads, if you come down to a bad main board, well you decide what to do if buy another one or try to fix it, there is a simple fix for it but i can't describe it sorry..
further tips to test it, locate the bad chip by freezing it with duster spray can, the freezed chip that permits tv to boot or work for longer is the defective one and you can also let to reball it from a repair center.. also the bad chip would get abnormally hot when tv is running "well"..

Hi, it's mostly between 20-25°C. It was standing for a few days, but with the casing on, so there was only restricted airflow. I will try letting it stand for some time with the covers off in the sun and then try again.

There was some oxidation on the upper part of the mainboard that I already cleaned, but that didn't cause any shorts (checked the caps and the transistors). I will attach a picture. Everything else looked good. Obviously, I don't know how it looks underneath the BGA. The only other mentionable thing would be that the thermal cooling pad from the MB chip crumbled off. The other ones on the TCON came off easily. I'm not sure if that is a phenomenon of moisture or simply more heat.

[Diah]

..

the worse scenario if you have moister went to Panel Module Edge boards.. the idea of EasyBone good that you flip it, but try to use Isopropanol 99,9% with spray to wash edge boards and let the alcohol go out as you flip it... then give the time for complete dry.

[Davi.p]

trust me, you don't have to see the oxidation, but is present!, bga balls became unusable, also the cooling pad disntegrated is a sign of very high temperatures.. or mostly direct oxidation of the pad (it is metal added and silicone can develop mould)

[ILoveZeroTwo]

Quick update for everyone who gave me their advice. I left the TV without a cover for another 10 days, replaced the broken cooling pad on the motherboard, cleaned the LVDS connectors with isopropyl and it is working properly again. It has worked for over 15 hours with no sign of a problem.
Thank you all for your advice.

[nomoresonys]

glad to hear it, your patience has been rewarded.

[Diah]

Quick update for everyone who gave me their advice. I left the TV without a cover for another 10 days, replaced the broken cooling pad on the motherboard, cleaned the LVDS connectors with isopropyl and it is working properly again. It has worked for over 15 hours with no sign of a problem.
Thank you all for your advice.

good done

[EazyBone]

Nice!! 🙂