Ok, i`ve got an update.
Today I bought a working SNES Mini witch came with the official AC Adapter.

i`ve connect the official ac adapter in my old SNES and now the constant buzzing noise is gone but still i don´t have any audio.
So, i'm thinking that maybe the problem are the capacitors.
But which ones? i don't see any capacitor in bad state nor Sulphated.

Any ideas?

Thank you for your time!