Samsung 70" UE70TU7100K no picture just backlight, part 2 - fixed with a mainboard from a 50" TV 

There was a fault caused by the mainboard, but I did not test in any other way. The problem came back after about 2 months after replacing the mainboard and turns out that the display, or display driver board, or COF have an issue. I did not check it further. Far too much cost for the customer, and a lot of time for myself while having too many jobs atm.

@@screen-protector i asked because I have the same problem , with the main board keep restarting , but if I disconnect the flex ribbon it will stay on but no image just backlight , i have taken a board from a 65 inch and still the same , so no matter what i do or what part i change it won`t work , i tested the power board but i do not have to much knowloadge how to do that , but with some youtube tutorials i manage to test some parts and the power supply seams good , but still i cannot figure it out what`s wrong , with the main board connected but if i put a piece of paper in the flex it will stay on and i can hear it working , but still no image only sound..i do not know what to do more

@@danel557 In this case it's an internal display issue, or the driver board fault which is connected to the display. It can end up as well as a rabbit hole ;). But, if you have time, you can check all the signals like VGH, VGL, you'll have VCC for sure, VDD and others. There's a problem in the LVDS, I'd not look on the mainboard or PSU anymore.

@@screen-protector manage to find the problem , with a small piece of electrical tape and few hours of pain i manage to find the faulty connection from display and cover it and now work perfect , no dead pixels no line nothing , i`ve been lucky

@@danielmoasa5734 awesome. I'm not always lucky with the tape, so good for you :).

For me, if you did change the power supply on an another known good one, it can be a backlight issue. The backlight is dying quicker in the newer TVs after 2, 3 years and I've seen it even quicker. To remove the display and replace it, you will risk it because the display is only 2-3mm thick. You can break it in no time. The first attempts are usually catastrophic ones. The backlight itself is not a big cost, but the job you need to learn or risk a whole TV. I'd not bet on anything else to be true - if you can trust the parts that you've replaced already ;).

Thank you so much for the prompt response, Peter!✨ Ah, that seems logical. Yep, the TV is thin... Do you know why the TV works over longer periods if I let it rest without the power cable connected for a week? My assumption is that the heat is causing a break in the backlight then, and the reason the TV is able to start is due to the high voltage at boot? I have seen a few backlight replacement videos on thicker TVs. I need to look into how it is done on thinner TVs. I experimenting with hardware, and I hope to get the same happy reaction you get when you manage to fix your TVs soon!😄

Do the backlight need to be of the same brand and model or is it possible to use cheaper backlights from third-party? Does it affect image quality or only brightness? I mean brightness will affect the quality too, but you get what I mean. Do HDR TVs have special backlight?

@@NinjaTurtlezz the cheapest way is to buy LEDs and solder them on your own. But, it's a tedious work and you need to have not only a time, but skills as well. This will cost you a few £££. You can use different backlight, but yes, this might affect the display quality after. Even if the voltage will be the same, colour might be different. But, if you'll use diodes with a different voltage, you can burn something. Plus, if you'll use a different model, you'll struggle with an installation after. So, the best way is to buy a full set and for not only the model, but for your TV. This is more than a model. Each model can have several types of the backlight :).

To jest problem z sygnalem LVDS, samemu tego nie ogarniesz raczej, chyba, ze masz duzo szczescia. Ogolnie to unikaj wszystkiego co nie Sony, albo LG, bo jakosc czesto kichowata, albo jak w Samsungach drogich dopiero cos mozesz znalezc lepszego. Jak masz kogos lokalnie, bo ja w Szkocji zaklad prowadze, to tam sie odzywaj, powinni pomoc ;).

A jeśli bym chciał sam to jakoś naprawić to co bym miał zrobić żeby odpalić go jakos bo taśmę też wymieniłem w tym tygodniu i to samo się jest nie daje wogule obrazu nadal

I jak pan myśli bendzie przy tym głównym co idzie taśmą od płyty głównej do matrycy ta co jest ta większa co idzie jako pierwsza to wejście czy te pojedyncze co są po bokach te mniejsze

@@Wariacikk696 jezeli chcialbys naprawic to samemu, to trzeba sie douczyc co to jest sygnal LVDS w telewizorach i jak odcinac uszkodzone sygnaly. To jest wiedza elektroniczna, takze tego sie mlotkiem nie naprawi. Albo sie to lubi i uczy, albo przypadkowo to mozna popsuc. Lepiej isc do zadkladu napraw RTV z tym uszkodzeniem. Bo jak sie popsuje, to potem mozna tego zalowac ;).

Udało się uruchomić ale teraz mam połowę ekranu ciemniejszą i mi się pasek pokazał taki czarny i tego układu jak dotykam to się zmienia obraz da sie to naprawić taki mały podłużny co taśma idzie od matrycy do tej płytki zielonej to jeden układ na tej taśmie od matrycy idoncej sie ten układ uszkodził