LG 55EA970V OLED / black screen

[pedrolane]

Re: LG 55EA970V OLED / black screen

I removed R7216 (100 ohms) and now LED_R is left opened, no more connected to LVDS pin 44.
Unfortunately it doesn t change anything. I can power on with P_ONLY but still no DRVON nor 12v on LVDS, and nothing on screen

[Diah]

Re: LG 55EA970V OLED / black screen

I removed R7216 (100 ohms) and now LED_R is left opened, no more connected to LVDS pin 44.
Unfortunately it doesn t change anything. I can power on with P_ONLY but still no DRVON nor 12v on LVDS, and nothing on screen

upload yours diagram and real photo of the 2 pieces which you wrote there are 12V on them... mark it on photo so we can analysis it

[pedrolane]

Re: LG 55EA970V OLED / black screen

ok guys. so here are a closed picture of the panel vcc circuit (this is a spare card have, R7216 is still there).

Please also find attached my measurements. I guess all is correct, but PANEL_CTL is near 0v. PANEL_CTL is PIN4 of MICOM.

I also put the schematics, in case you dont have it.

I dont know whether panel_ctl should be up after / before inv_ctl. But anyway, both are near 0v.

[Diah]

Re: LG 55EA970V OLED / black screen

check C2347

[dvadssc]

Re: LG 55EA970V OLED / black screen

Micom pin 16 is labelled LED_R which is connected to T_CON_SYS_POWER_OFF (pin 44 of LVDS). I put the schematics on post 31, there are some R and capa around.

Do you think I may "break" the copper path to disconnect this pin ? I can remove R7216 as well. I've never measured 3.5v on this pin, so not sure if this is a good way to go.

I put the "training guide" here. There are some useful infos.

Where did you manage to find these service manuals and the schematic diagrams? Would you be able to let me know the source for me to obtain the manuals for LG 55EC930T - TA? I've been having a similar issue and after certain diagnosis done with the support from Diah We believe that an SOS signal is generated by TCON is forcing shutoff the PS. Need to locate the PIN which is sending the sos signal.

Thanks in advance .

[Davi.p]

Re: LG 55EA970V OLED / black screen

You made the panel selftest that i suggested, the test gone well, so you must move to somewhere else to find problem, main board feeds power to tcon circuitry through 12v line, without that tcon can't diagnose panel problems nor self test, so no sos no fault signals, so my bets are, few money, all three mb are faulty of software, second bet is that tcon has software problems that can auto test panel but not elaborate data from mb, so mb stops tcon feeding.

[pedrolane]

Re: LG 55EA970V OLED / black screen

check C2347

@Diah : With digital multimeter in capacitor mode, I measure 0.190 uF for C2347 on all 3 MB I have.
(MB totally unplugged, no power). Obviously I didnt unsolder the Capacitor from board.

I ve also test in ohm mode, value goes from 0 to ~4Mohms, so the capacitor seems to charge then block current, as (I think) it is supposed to.

I dont know what other test I can do on this C2347.

@dvadssc
Sorry, I dont have a golden source for these manual. I guess you should find with Google. Try to use your mainboard part number instead of TV model.

[pedrolane]

Re: LG 55EA970V OLED / black screen

You made the panel selftest that i suggested, the test gone well, so you must move to somewhere else to find problem, main board feeds power to tcon circuitry through 12v line, without that tcon can't diagnose panel problems nor self test, so no sos no fault signals, so my bets are, few money, all three mb are faulty of software, second bet is that tcon has software problems that can auto test panel but not elaborate data from mb, so mb stops tcon feeding.

Yes, we thought MB was in "locked" mode. But we never managed to get out of this mode with P.Only on SVC remote, nor reset code etc. We also tried to reset MICOM with switch0 on MB. No luck.

I've already changed the TCON, without results. The second TCON is fine with self test too.
Is it possible the MB provide 12v to TCON for just some milliseconds, the diagnose an issue and shut the 12v ?
If you have any idea of test I can do, let me know.

[Diah]

Re: LG 55EA970V OLED / black screen

@Diah : With digital multimeter in capacitor mode, I measure 0.190 uF for C2347 on all 3 MB I have.
(MB totally unplugged, no power). Obviously I didnt unsolder the Capacitor from board

unplug the 4 ribbon between T-CON & Panel from T-CON side... and try all MB you have one after one to power it on with on with P.Only take always the optic audio out put as reference if it lit red. .. then you need to simulated to exit the test mode by S.RC as press exit and turn off ... then turn on normal.
this hope will help make the MB boards you have one come to normal mode

[pedrolane]

Re: LG 55EA970V OLED / black screen

So I've unplugged ribbons on tcon side, I only have 3 : 2 LVDS from MB + 1 20v power from PS

I've check with 3 MB, same results :
- I can power on with P.ONLY
- I have 3.5v on PWRON, 12v and 24v from P202
- but nothing on SPDIF output
- I have 5v on USB, IR service RC is okay, front logo is lighting on then off
- if I do nothing the set remains powered up
- if I p.only, then exit, then turn off (by unplugging from wall), nothing new when turn on, still nothing on spdif

the MB seems stuck in "defect" mode

[Davi.p]

Re: LG 55EA970V OLED / black screen

try this, mount and connect everything, turn power on, press or keep pressed one of the two buttons on mb, if nothing happens press or keep pressed both, do this with one of the replacement mb and original tcon since i suspect original mb was ko

[Diah]

Re: LG 55EA970V OLED / black screen

So I've unplugged ribbons on tcon side, I only have 3 : 2 LVDS from MB + 1 20v power from PS

I've check with 3 MB, same results :
- I can power on with P.ONLY
- I have 3.5v on PWRON, 12v and 24v from P202
- but nothing on SPDIF output
- I have 5v on USB, IR service RC is okay, front logo is lighting on then off
- if I do nothing the set remains powered up
- if I p.only, then exit, then turn off (by unplugging from wall), nothing new when turn on, still nothing on spdif

the MB seems stuck in "defect" mode

how about T-CON 12V still 0 or it went high at P.ONLY?

[pedrolane]

Re: LG 55EA970V OLED / black screen

try this, mount and connect everything, turn power on, press or keep pressed one of the two buttons on mb, if nothing happens press or keep pressed both, do this with one of the replacement mb and original tcon since i suspect original mb was ko

We already tried that. I tried it again without result.
The switch sw100 pull high on IC100 GPIO20 (debug pin)
The switch sw300 reset micom (i can hear the relay open / close)

how about T-CON 12V still 0 or it went high at P.ONLY?

Powered on with P.Only (or with ON button) I still dont have 12v on LVDS pins.
I do have 12v on 2 pins of Q2302 as measured a few days ago.

Now I'm wondering what the purpose of little headers P3000 P3001 P101 is. All of three have 4 pins and I can see in schematics that for P101 at least, there is some UART routing with GND, +3.5, RX and TX. That sounds familiar to me. I will try to plug a RS232 console cable on that, and see if something comes out at 9600bps. There are some mentions of RS232 tbshoot in manual of a quite similar LG board, however my MB does not have an obvious RS232 connector (DB9 for example).
Are you guys aware of troubleshooting this way ?

[Diah]

Re: LG 55EA970V OLED / black screen

We already tried that. I tried it again without result.
The switch sw100 pull high on IC100 GPIO20 (debug pin)
The switch sw300 reset micom (i can hear the relay open / close)



Powered on with P.Only (or with ON button) I still dont have 12v on LVDS pins.
I do have 12v on 2 pins of Q2302 as measured a few days ago.

Now I'm wondering what the purpose of little headers P3000 P3001 P101 is. All of three have 4 pins and I can see in schematics that for P101 at least, there is some UART routing with GND, +3.5, RX and TX. That sounds familiar to me. I will try to plug a RS232 console cable on that, and see if something comes out at 9600bps. There are some mentions of RS232 tbshoot in manual of a quite similar LG board, however my MB does not have an obvious RS232 connector (DB9 for example).
Are you guys aware of troubleshooting this way ?

its impossible all 3 MB had same defect..
1- use the t-con you showed me before with burn image no signal
2- yours info always not complete.... now i do know no Panel 12V when you Use P-ONLY or normal ON.. but what about DRV_ON. are there signal go to PSU and u have on T-CON the required currents ?

Tv will turn on with out the socket of 20-24V from PSU to T-CON driver boards. so plug the LAN cable with yours router. and check if there are assigned ip for the TV.

if there are no DRV_ON you need to check the sockets at MB side.... because when you do standalone test PSU work normal.

[pedrolane]

Re: LG 55EA970V OLED / black screen

Again, thanks for your time

its impossible all 3 MB had same defect..

Yes, that seems quite impossible

1- use the t-con you showed me before with burn image no signal

That's the one in TV set right now, but it is unplugged as asked (both LVDS and 24v)

2- yours info always not complete.... now i do know no Panel 12V when you Use P-ONLY or normal ON.. but what about DRV_ON. are there signal go to PSU and u have on T-CON the required currents ?

No DRVON on MB, so no DRVON on PSU. So no 20v nor 24v from PSU. So no voltages on tcon. I never never never saw any MB put DRVON up.
The only way to power the tcon is to force DRVON on PSU AND brings 12v on LVDS fuse at the same time.

Tv will turn on with out the socket of 20-24V from PSU to T-CON driver boards. so plug the LAN cable with yours router. and check if there are assigned ip for the TV.

With LAN plugged in the interface comes up (5v) but no negotiation, no arp, no dhcp, no ip. It's like the MB : powered on but uninitialised

if there are no DRV_ON you need to check the sockets at MB side.... because when you do standalone test PSU work normal.

DRVON is INVCTL on MB. I can see it on R7204 (pin 6 of first LVDS).
And it stays at 0v forever.

I saw in manual that MICOM monitors 5v and 12v, and it will shut down if missing.
My MB does not shut PS, it just doesnt boot ... So PSU and connectors seem fine.

What about the serial RS232 check ?

[Diah]

Re: LG 55EA970V OLED / black screen

What about the serial RS232 check ?

try to capture the boot log it will help too

[Diah]

Re: LG 55EA970V OLED / black screen

by the way... lets forced the MB ..
slide out the wire of DRV_ON from the PSU socket ( be sure isolated it that didn't make contact to any part or chassis)

jumper Power_ON to DRV_ON..

all LVDS ribbon t-con 24V etc should be in place as original.. turn it normal and check panel 12V.... 24V t-con and the 20V to MB also see what the screen will display in case the panel 12V work again

[Davi.p]

Re: LG 55EA970V OLED / black screen

usually uart connection on tv are at 115200, but you must use a special adapter for 3v rs232, a ch341a programmer is ok. You will not find much informations on the log i think, you must first ensure that flat cables between mb and tcon does not have bent touching pins..

[pedrolane]

Re: LG 55EA970V OLED / black screen

usually uart connection on tv are at 115200, but you must use a special adapter for 3v rs232, a ch341a programmer is ok. You will not find much informations on the log i think, you must first ensure that flat cables between mb and tcon does not have bent touching pins..

I have several usb ttl adapters. I've used one based on Prolific PL2303HX chip, which is designed for 3.3v arduino. Product page here
So I plugged RX TX and GND to header P101.
While I can see receive garbage, i can't find anything useful. I have 1 byte of data each time I send a carriage return, thats all.
I tried at 115200 8N1 and various other settings on speed, data bits, parity and flow control without luck. Not sure this debug mode is enabled at all at it seems there s nothing on these uart pins.

by the way... lets forced the MB ..
slide out the wire of DRV_ON from the PSU socket ( be sure isolated it that didn't make contact to any part or chassis)

jumper Power_ON to DRV_ON..

all LVDS ribbon t-con 24V etc should be in place as original.. turn it normal and check panel 12V.... 24V t-con and the 20V to MB also see what the screen will display in case the panel 12V work again

I didnt try yet but if I force DRVON on PSU it will deliver 20v to tcon, but 12v on MB will still be absent from LVDS. So no 12v on tcon, no screen. Am I wrong ?
Or you want to force DRVON/PANECTL UP on MB side ?

[Diah]

Re: LG 55EA970V OLED / black screen

I didnt try yet but if I force DRVON on PSU it will deliver 20v to tcon, but 12v on MB will still be absent from LVDS. So no 12v on tcon, no screen. Am I wrong ?
Or you want to force DRVON/PANECTL UP on MB side ?

we will be close to know where are the matter... also only DRV_ON wire slide it out from the PSU socket.. and jumper the DRV_ON pins with Power_ON. all cable should be in place.