[Solved] Samsung UE55F9000 - black screen, no backlight, unable to start, LED

Hi

I have a problem with the UE55F9000 TV.
As my wife says (because I was not at home then), my two-year-old son got the remote, clicked something on the menu and the TV turned black. I don't believe it a bit, but I swear that it was so, and the TV is hanging on the wall, so my son has no chance to reach him.

Currently, the TV only has a white light after turning on the power, as if it was turned on and when pressing the buttons on the remote control, the red LED flashes, besides, the screen is completely black, even the backlight does not work.
After disconnecting the smart box, the TV turns on and off with the remote control (the white light goes out), the rest of the symptoms are identical.

Main board BN-01950C
Logic BN-02076
tcon VD_556EU22BC6LV0.1
PDU L65D2L_DSM BN-00675A

Any suggestions are welcome.
best regards

Can you enter "service mode" ?.
If so, perform a factory reset.

The TV does not display anything even the logo: - /
The backlight does not turn on and when I put the flashlight on, the matrix is dead.
The only idea I have is to replace the motherboard with another used one.

Motherboard and power supply replaced, but unfortunately no effect.

What should the TV display without one connect connected?

For posterity, the disc with the matrix logic was a problem.

Everything works after replacement

For posterity, the disc with the matrix logic was a problem.

Everything works after replacement

Added after 33 [seconds]:

Exchange of matrix logic