Screen backlight flickering also in the Bios

[Antonino5]

 Hi at all!

Since some time,  my laptop screen present this issue: the backlight “in the central part of the screen” flickers. 

This happends both the battery and the ac plug. 
Firstly, i tought that the cause was the driver in windows 8.1 .. because initially the issues the flickering it happened only with the ac plug (or without, i dont remember). So i looked for gpu/battery/acpi drivers, changed everythings, re-installated win 8.1 but nothing.

In these days, while i worked to restore my hp, i spent a lot of time in bios boot screen, “windows is loading file” screen, different hard disk, different OS, live linux cd,(…) , and I understood that the flickering problem is present too in the bios and in every condition.

I tried if the issues “change” moving the screen, but no.

Only difference is  when i decrease the brightness, and the flickering stop.

What can be the problem? Inverter, backlight or the cable? There is some test to do?

I don’t think the problem is the cable because moving the screen nothing happends, but i don’t know.

There are many videos on the web, i can paste the url with most similar effect?

EDIT:

If i disconnect this pin while pc is on, the backlight turns off, but the display still on (you can see the hp logo of the wallpaper), and with a torch i can see everything.

Any idea?