Sharp Aquos LC-40UG7252E LCD TV burn in?

[jonah1024]

Hello!

I'm a few days old into this TV screens repair universe so please bear with me.

Recently, and all of a sudden my 40” 4K Sharp Aquos LCD TV turned on with colors all smudged in some places on the screen that remain like that even without any kind of video source. I do have image but the colors are smudged/tinted/ washed out in patches as per defects. This to me looks similar to burn in but I'm shore this is not an OLED.

- I did the classic unplug and hold power button to discharge the caps but it didn't help.
- I did a factory reset as well - no change.
- I also started to measure some voltages from the main PSU and I get stable voltages (5v, 12v).
- I also measured most of the labeled test pads on the scalar-T-con combo board and I get stable 1v8, 3v3, 7v and 12v.

I tried doing the tape trick to narrow down the issue but the panel ribbon cables are soldered to the scalar/T-con board so I can't do that.

The backlight seems to light up uniformly if I block the video signals on the LVDS cable

I've searched online, on this forum and on a couple of electronics discord servers but I haven't found a similar issue anywhere.

Any tips or ideas on how should go about diagnosing/fixing this?

Thank you very very much.


PS. The attached video shows the burning/preshipping mode I enabled to see how the defect behaves on all colors.

[Davi.p]

i suspect main board, must perfom the stand alone panel test,
unhook lvds from main board, jumper the 12v from PSB to tcon 12v in..

[jonah1024]

Thanks for the reply. What should I expect/ look for with the 12v jumper? 🤔 I did some measurements before and I do get stable 12v on the T-con board.

[Davi.p]

it"s a video test, full screen Red, green, blue, white..

[jonah1024]

I did the video test, as shown in the video attatched while in the factory menu. Is this different? I also managed to trigger the video test while taping the LVDS in different locations and the colors look the same. If I already get 12v on the T-con why do I need the voltage bypass?

Sorry for all the questions, I am trying to understand the process.
Thank you!🙏

[Davi.p]

there's no attachment... i don't know if it's the same, it is better as i have told, the panel if it receives power but not signals goes in to test mode, redo it and tell if it is flawless, i don't like downloading videos if possible, except streaming YouTube..

[jonah1024]

Here is the test mode video:
https://youtu.be/VNk8TkR7h_U

[Davi.p]

OK, first this is a screen problem, MB is OK, i see there is a constant pattern, this tells me there is maybe an error in the TCON DATA, thus the content of the flash..
if you haven't already did, udpate the TV, if the update contains TCON changements, then MB will rewrite TCON data.. in desperate case could be useful downgrade the MB soft by direct flash programming, if no go then maybe udpate it again

[jonah1024]

Thank you!
I will attempt a motherboard firmware upgrade/reinstall (I'll look online for the firmware or ask Sharp directly) then attempt a downgrade, and if that fails to fix the issue I will look for a T-con firmware and do a direct flash if possible (either jtag or desolder the rom flash).

I see the scaler/T-con board has a Samsung VTU63A0 display chip, two DC-DC ICs (RT6939 and RT6935) and a winbond spi flash.

I will document everything and be back with updates as soon as possible.

Thanks again! 🙏

[Davi.p]

.

[Davi.p]

.

[jonah1024]

I don't think I got what you meant. You want me to check for short circuits between the SPI flash pins?

[Davi.p]

sorry forget this part for now..

[jonah1024]

[UPDATE] with new symptom:
I just came back after a 2 week holiday while the TV stayed unplugged for the entire time. I plugged it back to investigate the problem and there was no problem!!

Image was back, sharp and clear.

HOWEVER, after the usual ~3 min timeout it shut itself off and after I rebooted it back the image problem returned, same defect as described above.

Can this still be related to a software issue? My newbie gut feeling is telling me that it might be a “bad cap” somewhere?

[Davi.p]

locate the tcon flash memory, remove entirely its solder and resolder it.

[jonah1024]

The memory chip is a winbond 25Q16JVIG which uses I think a WSON8 socket with a big underneath ground pad and no little feet (I've attatched closeup pictures).
I don't see any signs of bad soldering between pads and pins but I will try to reflow the solder as careful as I can to rule that out.

I also upgraded the NAND firmware from v4.58 to v4.68 using the usb flash but the problem did not go away. Most likely as you said it did not have to upgrade the T-con memory at all. I can't find old firmwares unfortunately, I've contacted Sharp but still waiting for a reply.

Any other ideas?

Really appreciate the support!
Kind regards,
Iona

[Davi.p]

Be gentle... why you say "reflow" ? my advice is different..

furthermore, i see like a glue around the tcon FPGA chip (main chip), i see well? Are there any other big IC on there? Can you photograph it?

[jonah1024]

I just feared I might mess things up but will add some kapton tape all around and see what I can do.

[Davi.p]

Ok is a difficult task, my advice, start by steps, first one, add new solder, remove it the best U can with copper braid, put new solder..

[jonah1024]

Hi, I did what you said, desoldered cleaned, resoldered, The problem is still there. I also dumped the spi flash just in case.