MacBook Pro 2011 no display signals

hi guys... so i'm doing some maintenance in this late 2011 mackbook pro 15'' machines for my courrent enterprice.

ok i'm not an expert but i think this issue is kinda odd to me, here is what is happening:

1.- this mac book pro chimes and after loading the keyboard turns on which means the computer is actually working

2.- theres no signal in any display, no signal in macbooks pro display or external monitor.

3.- the macbooks pro monitor actually works fine (i tested in other macbook pro 2011)

4.- i tried NVRAM reset and SMC reset (though i dont really know if i'm doing it right) and nothing happends

5.- the back light fuse works fine as it closes the circuit, i have no luma and no chroma and no power in the display

so..... i dont know if it could be the GPU chip (for a chance, a lot of this computers fails with that) or a hardware problem and if not, what else i could do to make it works