LG 49UK7550PTA - after couple of hours screen starts to blink

[JohnML1975]

Hello Forum team

Have this TV; searched for the model and could not anything so thought I would share in here

Had an issue, some years ago, and looks like some placed sticky tape over some of the lines on the FFC cables between the T con and the mainboard
Anyway, the owner, who gave me the TV, says it starts to blink after a few hours

So I removed the covers, and could not see anything visibly
Removed the power supply and thought some of the solder joints, on the hot side, were not the best. I thought some looked like they were cracked.
So I resoldered any joints that did not look good

Then I turned TV and noted some diodes did not look the same temperature and I replaced these with new
New ones look the same as the old ones under thermal camera

Anyway; since I did the soldering and did the new diodes I have not run the TV for a few hours and experienced the blinking
So I am going to try that next and share the outcomes here.

Shall welcome any inputs or experiences you all might have.

Thank you

[JohnML1975]

Photos thus far.
The diodes, or the area around them, appears to have been hot. They measure okay, or the same, as far as I am concerned but I replaced with new anyway.

[JohnML1975]

Update on this one

With the new diodes I do not note any temperature difference

Have been running the TV for fours now
Yet to see any blinking and I should have by now

I guess the factory reset and the re-soldering of the joints may have resolved this TV

will do another five hours of testing

thank you

[howardc64]

Probably good to clarify what is "blinking" but sounds like you've not seen it. Backlight blinking and LCD panel blinking would be very different problems.

Those 4 diodes you changed looks fairly close to the backlight output connector and after the backlight voltage transformer. I'd guess they are on the output path to the LED power rail. I recently fixed a LED TV PSU with shorted diode in the backlight output path ( barrier rectifiers link ) I ended up replacing the entire board set (main, zoned LED driver, PSU) due to Samsung's firmware update that killed the dimming backlights + max brightness only. Which probably is what killed the LED voltage output section of the PSU.

T-Con to buffer board flex tape masking is still there? Likely solving a short on the panel and/or panel's edge buffer board.

[JohnML1975]

Hello Howardc64

Thank you and I had read your post a few days ago

The flex tape is still there from a previous repair and I shall leave it there.
No doubt you are correct on this point
It looks like the tape has been heat welded and not easy to remove
So I want to leave that alone

For the blinking I have not seen and I am five hours into testing

Let us see how I go

again, thank you