Samsung UE50KU6070 black screen

[totof]

Hello,
I have my TV model UE50KU6070 which I am trying to repair.
BN41-02528A / BN94-10800C motherboard.
If I disconnect the motherboard from the power board, the backlight works. When the motherboard is connected the backlight works but the screen remains black.
When I plug the TV into the electrical outlet, the standby LED lights up but no reaction to an attempt to start it with the remote control for about 1 minute. During this minute the TV consumes about 20W.
After one minute the consumption drops to 0W and the TV can turn on with the remote control but the screen remains black. All voltages on the motherboard are correct.
The TV turns off with the remote control but you have to wait about 1 minute before restarting it again. Sometimes at startup the screen displays "Samsung Smart TV" for 1 second before going black.
In fact, in addition to the black screen, it is as if the TV was extremely slow.
The behavior is the same if I disconnect the two LVDS cables.

Do you have an idea of the problem and do you think that the motherboard is repairable for example by reprogramming the memory?

Thank you in advance for your help.

[CapLeaker]

Re: Samsung UE50KU6070 black screen

Reflash the SPI or whatever it is. Looks like a good candidate, at least it’s worth a try if you can find a dump file. Also check the SPI first, before you put a new file on. Not that you have a bad one.

[totof]

Re: Samsung UE50KU6070 black screen

Thank you CapLeaker.
Attached the SPI file but i have no idea whether the content is valid or not.

[CapLeaker]

Re: Samsung UE50KU6070 black screen

read the spi, save a copy, FF the spi and check it. Hopefully it is still good, then all you need is a working dump.

[totof]

Re: Samsung UE50KU6070 black screen

SPI seems good, I wrote FF without problem

[Davi.p]

Re: Samsung UE50KU6070 black screen

it is not a memory problem, must be checked the entire psb with dummy loads

[totof]

Re: Samsung UE50KU6070 black screen

it is not a memory problem, must be checked the entire psb with dummy loads

It is very interesting but I don't know how to this check.
All the voltage on self components seems good.

[Davi.p]

Re: Samsung UE50KU6070 black screen

you don't know ohm's law? It's hard starting whatever repair without it , must collect some power resistors and a lamp..

[totof]

Re: Samsung UE50KU6070 black screen

Thank you Davi.p
For the ohm's law it should be fine but the problem is that without a diagram of the card it is very difficult for me to know what to test.
I have already checked all the voltages on the inductance and they are OK. No shorted capacitors either.
What I would like to test are the signals to the LVDS cable but without a diagram it's complicated

[nomoresonys]

Re: Samsung UE50KU6070 black screen

backlights and powerboard are fine, proved by results of first post.

[nomoresonys]

Re: Samsung UE50KU6070 black screen

maybe try the tape cut-off method just for fun, never know when it will work.

[nomoresonys]

Re: Samsung UE50KU6070 black screen

Capleaker probably nailed it with post #2, eeprom/spi/nand dead.

[Davi.p]

Re: Samsung UE50KU6070 black screen

maybe we don't understand ourselves, i suggested you to test the power supply outputs, that are usually marked on board each signal, put a resistor on the 5v, a lamp on 12v and so on..

[totof]

Re: Samsung UE50KU6070 black screen

I rechecked all the voltages on self and they are good.
VON, VCCA, VCCB and AVDD voltages are also correct.
I just bought another motherboard pulled from a broken TV and the TV works again.