LG 86ul3e-t logo blinks and then nothing (but backlight stays on)

[Panczis]

Re: LG 86ul3e-t logo blinks and then nothing (but backlight stays on)

In post #11, on the picture driver_3_1.jpg are the two ribbons that goes to the TCON. But each pair of the driver boards is connected with the mentioned "U-ribbon". You can see the connector on the pictures "driver_3_4" and "driver _4_1".
@budwich: Thanks for the hint, I will try that. I afraid, that the broken driver is the third board, so if it is a first in line, from the TCON, than it will not start until I find the fail. I thought that with two sides of the panel, when I disconnect the half, I will get a part of the screen on. But only when all four ribbons are conencted, the logo apears. Probably the whole panel must be operational to get the proper picture on the display

[budwich]

Re: LG 86ul3e-t logo blinks and then nothing (but backlight stays on)

the problem with the "gross disconnecting" of the tcon to panel cables, you loose a lot of the signals that are required for the "sanity" of the system. By doing a smaller subset of the hardware "isolation", you have a better chance of getting some where in terms of system startup. Your pictures seems to show a problem more on the side than the bottom... my guess.

[Diah]

Re: LG 86ul3e-t logo blinks and then nothing (but backlight stays on)

well i never saw LG panel display logo then go protection because of driver even if the screen smashed it will display and never send signal to shut down.. but LG mainboards it function with specific IR code signal, same to lg OLED even the original RC cant turn it on but service remote turn it with power only..
this why i went to inspect the RC of this set and the operation manual of it... it till same story i writing it now.

[Panczis]

Re: LG 86ul3e-t logo blinks and then nothing (but backlight stays on)

I'm back, with some success
I was able to run the LCD panel, so it doesn't stops anymore. What was done? I have blocked a error signal from the panel driver to the t-con board. With a scotch tape I blocked first 10 pins on the third ribbon, which connects the t-con and panel driver boards.
TV started, but I had to reset it wit a service remote control, as it was in the power only mode, after my previous actions. I'm attaching the message that was shown by the TV in this state. It shows the software version and a short guide how to run it to the user menu. Now I have the picture from the external source (laptop with HDMI output).
Probably I can see now, why it goes to the protection mode. There is a blinking line at the top of the screen. I made a video, how it looks.
So now I need your help guys. What should I try to check, to identify the root cause of this blinking line. The line is visible only on the bright background. With a Youtube menu, or when the black backgroud is displayes, all works fine.

Here is a link to the movie: https://photos.app.goo.gl/U6vQdPyucHBjrHT57

[Diah]

Re: LG 86ul3e-t logo blinks and then nothing (but backlight stays on)

I'm back, with some success

can you make remark of the 10 pins you blocked at T-CON ribbon on yours T-CON Photo

[Panczis]

Re: LG 86ul3e-t logo blinks and then nothing (but backlight stays on)

Take a look at the attached picture. It seems that the most important is PIN-9. I realized that the VCC is lost, after a first 2-3 seconds, when the display boots up, and shows LG logo. On the 9-th PIN must be an error signal, because a signal appears on it, after the VCC goes to 0V. It was hard to mask only the one PIN, so i decided to mask a few first pins. After this trick, it started to work.
Now the only problem is this blinking line. Any ideas how to start? Probably it may be a bad capacitor. You are more experienced, could you advice me what to do?

[Diah]

Re: LG 86ul3e-t logo blinks and then nothing (but backlight stays on)

Take a look at the attached picture. It seems that the most important is PIN-9. I realized that the VCC is lost, after a first 2-3 seconds, when the display boots up, and shows LG logo. On the 9-th PIN must be an error signal, because a signal appears on it, after the VCC goes to 0V. It was hard to mask only the one PIN, so i decided to mask a few first pins. After this trick, it started to work.
Now the only problem is this blinking line. Any ideas how to start? Probably it may be a bad capacitor. You are more experienced, could you advice me what to do?

so as you wrote pin 9 was active at time vcc cut off, so its sending SOS signal.. normally SOS signal will turn off the T-CON first. as i remember you wrote before you owned another T-CON, so with it trace the connectivity of this PIN9 if it goes to SPI/eeprom on T-CON via L or R

[Panczis]

Re: LG 86ul3e-t logo blinks and then nothing (but backlight stays on)

The second t-con works in the same way. I think that I will try to look for the broken cap right now.
The screen works, but there are horizontal stripes visible on the left side of the panel. It is visible only from a short distance

[budwich]

Re: LG 86ul3e-t logo blinks and then nothing (but backlight stays on)

does the "U" cable test that I suggested earlier have any impact on the display IF it does work.. or the panel does not work without your "tape mask trick"? It might help in determining if there is some smd cap on the driver board that is a problem.

[Diah]

Re: LG 86ul3e-t logo blinks and then nothing (but backlight stays on)

i dont think there are any shorted smd.. its open circuit at the panel .. so the t-con shutting down.. i faced once with 65 4K made by vestel with LG IPS panel, there was small broken at right corner down on lcd glass which it break one line on the thin film print circuit under the glass , when i terminated this part the T-CON start working..

[Panczis]

Re: LG 86ul3e-t logo blinks and then nothing (but backlight stays on)

does the "U" cable test that I suggested earlier have any impact on the display IF it does work.. or the panel does not work without your "tape mask trick"? It might help in determining if there is some smd cap on the driver board that is a problem.

The problem is in the third driver so the U ribbon doesn't affect the display. When it is disconnected, than there is no picture on the display. The line which blinks is not broken from any sides. I will try to fix the masking, to disable only the 9th pin, to chceck if those vertical lines are show due to masking too mamy pins.

[budwich]

Re: LG 86ul3e-t logo blinks and then nothing (but backlight stays on)

ok... thanks for trying this. Just ensure we are on the same page. You did the disconnect of the "U" cable without the tape in place or with the tape in place? You are certainly close to getting this working well. Hopefully the last step is within sight. good luck.

[Panczis]

Re: LG 86ul3e-t logo blinks and then nothing (but backlight stays on)

Thanks for all the hints.
Yes, with the tape or without it, when the U ribbon was disconnected, the screen was not working. Only the backlight started to work, but there was no LG logo shown up.
I'm quite happy with the current results, as I spent only 120Eur for the TV and list additional 150Eur for the parts. The bonus parts I will try to sell, as they were not needed.
Those thin lines are visible only from a really short distance. It was really exiting to learn how all those elements works togeter.

[nomoresonys]

Re: LG 86ul3e-t logo blinks and then nothing (but backlight stays on)

Another nice save, glad that monster didn't go to the landfill.