LG 55EA970V OLED / black screen

[pedrolane]

Hi

I've found lot of help here with already answered questions, but it seems I'm in a different case.

My LG 55EA970V OLED screen from 2013 was working well and stopped suddenly while in use, with black screen / no more audio. This model is quite unusual here in europe, so I didn't manage to find someone to help (tv shops etc).

I've already checked the following :

• power supply out voltage is fine at 3.5v 12v and 24v pins on the main P202 connector (picture attached)

• when powered on by remote I can hear the relay "click", the LG logo lights on, then the PWR_ON pin switch to 3.5v at P202 connector (picture attached), but no screen display (and no sound)

• the DRV_ON pin remains at 0, so there is no 20 volts at the bottom connector (P201)

I thought the main board was faulty, so I ordered a (used) one from a China supplier, but the result are the same (first PWR_ON, then no DRV_ON).

I had chance to also get another power supply board, so I've changed it too ... with the very same results.

I've followed part of the SMPS test document, but I can understand what component can be faulty. Is it possible that as the TCON remains unpowered, the main board considered it as faulty and turned into a "fail" state, refusing to start ?

While I can change the TCON too, I can't understand why the DRV_ON remains off.

I've also tried to plug a USB key with a small led indicator, thinking it may light up if the main board boots. But whichever port I use, the key remains off. So I guess the main board (old one or replaced one) does not boot.

I've noticed 2 little switchs on main board. The first seems to power off the device, but I can't find any doc regarding the purpose of these. I can't see any led on the boards, I don't know if there is one supposed to blink / light up.

I'm not quite sure about the "no sound" assertion as the TV was setup with external amp (through) ARC, so the embedded speakers may be disabled.

Will much appreciate any help from electronic warriors here !

[pedrolane]

Re: LG 55EA970V OLED / black screen

Also I've forgot 2 informations.

I got a lg service remote, so I'm able to use power only and in stop functions. I didn't try any for now as the screen remains black, I wouldn't see what I do ;-)

I plug the ethernet port to a switch and the led lights up on switch side when I power up the TV set.
So at least the mb "makes" something different when powered on.

However still no image nor sound.

[Diah]

Re: LG 55EA970V OLED / black screen

unplug the 20V socket from T-CON side --start the Tv with power only . screen remain black... then press exit on service RC. plug tv out from wall ( never turn it off with RC.) wait 1 minute and plug it in wall again ... main boards will start but screen black.... press IN_STOP on service RC. followed with code 0413 tv will go to STBY plug it out again from wall and wait little time then plug it in... main boards will reset to factory condition and you may hear sound of the start install..... while it is in this condition you can plug back the 20V socket back,. screen will come for short time on ... or if you are lucky will remain on if there are easy short on it.

[pedrolane]

Re: LG 55EA970V OLED / black screen

First of all, thank you for your time

I've made these very steps with 20v power ribbon unplugged on tcon side.
Plug the set (relay click), power only button (another relay click), then exit on RC, then plug of the wall.
After 1 minute I plug it back (relay click) but it doesn't power on. I've check the pwr on pin, still 0v.
I've made these steps several times, with the 2 mboards I have, same results.

If I force power on by touching below the LG logo, I can see it is on (logo lights, ethernet up, pwron 3.5v).

Then I tried instop button + 0413, it never goes back to stdby

I unplugged it anyway, then plug again, remains stby until power on. And then no clue of any factory reset (no sound no screen).

All of that with tcon unpowered.
By curiosity I've also tried with the 2 lvds cables unplugged, same results.

Can't understand ...

[Diah]

Re: LG 55EA970V OLED / black screen

did yours Service Rc working !!!! or are you sure there batteries inside it lol

post photo for all boards together to see how they are connected.

[Davi.p]

Re: LG 55EA970V OLED / black screen

Hi, i don't know these LG sets but i'll try to help you anyway, ensure your original power board is ok by testing it by itself pulling pwr-on and drv-on to standby voltage 3,5v and test the board outputs, besides you can test the main board watching the optical port red state and plugging an headset and selecting with remote or local keys the tv programs until you get one audio, terrestrial antenna must be in, hoping someone haven't had you make a factory reset. Check also if standby light glows with remote pulses.. aftter this you can try a tcon self test maybe, by unplugging only mb-tcon lvds cables and forcing psb outputs..

[pedrolane]

Re: LG 55EA970V OLED / black screen

RC seems fine as led blinks with every button press
And the TV powers on when using power only and power on buttons. However it doesn't seem to accept any other command.
Mine is VINABTY MKJ39170828 (image attached)

I will make some pictures of the whole setup, but don't expect any surprise. The boards are in place, connected with original ribbons.

I will try to shunt the Drvon to check whether 20v is okay on PSU.

[pedrolane]

Re: LG 55EA970V OLED / black screen

Here are the pictures, hope you can see clearly the details.
I try to expose the ribbons so as you can figure what go where.

This mb is the used one (some rust on connectors), but mine is fine.
The white ribbon at the bottom of mb is my rj45 to switch

[pedrolane]

Re: LG 55EA970V OLED / black screen

@Diah @Davi.p thanks for your time

I've just made the test for the pwron+drvon @3.5
I measure 19.9v at the p201 connector (tcon power supply). So I guess my PS is okay.

So the main symptom remains that the MB dont set DRV_ON to up, and I see this with

• any of the 2 MB I have

• with / without LVDS plugged

My guess is that the MB waits for some "okay state" from TCON before doing anything. So either the TCON is faulty, either it can't start with LVDS unplugged.

I dont worry about a factory reset as I make my test with a used MB with unknown settings. Also I dont have any hertzian antenna, and morevoer it wouldn't work without setup (channel scan).

I plugged in a satellite receiver via HDMI1. The receiver is on and working (tested with another TV set). I tried to power on the LG, switch to HDMI1 with service RC, but no sound in earphones/jack nor TV speakers.

What I didnt try for now is to put back the TCON power ribbon WHILE forcing DRVON. I love fireworks but my house is not the best place to enjoy it. Is it worth / safe to try ?

While ON the MB shows some activity on Ethernet. I cant see any on optical output. I will put a optical cable in it and check if I can see some light.

[Davi.p]

Re: LG 55EA970V OLED / black screen

the first test to be made is to disconnect mb from tcon and test mb as i have said, hoping your remote is ok

[pedrolane]

Re: LG 55EA970V OLED / black screen

@Davi.p I've already made this test.

All plugged in BUT lvds (the 2 blue ribbons from MB to TCON)
The MB start (pwron up and partial ethernet activity), but no sound on jack / speakers.
No leds on MB, dont know if it is supposed to show something. No USB activity.

I've tested with sat receviver on HDMI1, then played with RC (hdmi1, vol+).
Seems like the MB put itself in a powered on but standby mode.

You said "forcing psb outputs", cant figure what you mean.
The RC "should" be okay as some buttons work, but I cant be 100% sure

[Davi.p]

Re: LG 55EA970V OLED / black screen

psb is the power supply board , actually you can totally disconnect mb, jump pwr on/ drv on to standby 3,5v then hope an image appears on the screen, rgb test, i don't know if this way the 12v is fed to tcon, if not you must jump a wire to the tcon fuse..

PS: ok watching the photos the 12v is fed to tcon by the mb, but the mb is disconnected so you must jump a wire at least 0,50mmq from psb to tcon fuse near the mb-tcon connectors, use the fuse terminal torwards the connector

[pedrolane]

Re: LG 55EA970V OLED / black screen

Is it safe to force the TCON up by providing 20v / 30A giving it may have shorts ?
I cant see the fuse on TCON side for now, I guess I have to extract the TCON (it is behind a heavy metal plate)

I didn't do the test of having all plugged in + force DRVON
Isn't it a safer way to test TCON ?

[Davi.p]

Re: LG 55EA970V OLED / black screen

The tcon fuse is there to protect the tcon, further each dc dc converter has surely a sc protection, so no risks, other thsn a fuse

[Diah]

Re: LG 55EA970V OLED / black screen

don't do this in this way..
MICOM- on MB went to sleep safe mode after there are SOS signal come from T-CON driver boards regards to Panel state.
my post #3 can be used to terminated this mode. but it went wrong with you reason unknown to me.
so do this instate.
let all socket in place as original. the wire of DRV_ON pull it from the socket at PWB side. jumper the pins of DRV_ON with 3.5V. turn on the MB will have 12 / and 18 for audio and the T-CON will have 20V too see what will you have on screen and optical ports only.

[nomoresonys]

Re: LG 55EA970V OLED / black screen

Listen to Diah, he does things the SAFE way, davi does NOT.

[pedrolane]

Re: LG 55EA970V OLED / black screen

I respectfully thank anyone that takes time to help me here with this issue, even with not so safe ideas :-)

So I make the full test, all plugged, just forcing DRV_ON to up, and nothing changes.
On power on I have 3.5v on PWRON, DRVON, all voltages okay, and 19.9v ready for tcon.
But screen remains black.

I also plug a spdif / toslink on MB, but cant see any light on the other end.
So the only sign of life is the ethernet port that is UP 2 sec after power on (but no activity / no ip) and the voltage on PWR_ON pin.

I might be able to get a used TCON, so I will try to swap as soon as received.

If any interest I have the service manual here. It says to make all the tests I've done so far.
I also saw that there is some some of RS232 feature. May a try to connect with serial ? Can it be of any help (diagnose, factory reset) ?

[Diah]

Re: LG 55EA970V OLED / black screen

from yours photo it show you never take the heat sink of the T-CON. and also maybe you never tested the 20V fuse & 12V Fuse on it.
if this the case. then you are diving at wrong ocean and you brought us with yours diving.

[pedrolane]

Re: LG 55EA970V OLED / black screen

While i would love to make scuba diving with you, be sure I did remove the backplate and test the fuses on the tcon (as well as fuses on PS)
I put it back all together because I worry about heat dissipation on tcon.

Anyway, with TCON totally disconnected from MB and PS the whole behaviour seems strange. Isn't the MB supposed to boot ever without tcon ?

So the only remaining cause is that the Mb never exited the failsafe mode and my service RC is faulty, and I should find another one.

[Davi.p]

Re: LG 55EA970V OLED / black screen

my advice unsafe? I don't think, you can continue buying boards, you never know if them are ok until you see tv working, you must pretend boards from working sets but maybe someone can lie.. brand new boards manufactured only for spare parts are a fable 4 me..