Xbox 360 doesn't turn on

Hi guys, i bought a broken xbox 360 (MW3 edition). When i press the start button there is a sound from the internal speaker that i can describe as a loud hiss that fades away quickly.

This means that there is no light, neither red nor green, the console does not turn on and the USB does not receive power. Perhaps the problem is the power brick, with a multimeter I could verify that it sends the 5 volts of standby and the orange light remains fixed. Maybe it is not sending the 12 volts for the console to start, is there a way to send the 12 volts directly to the board? I have a 150 watt multivolt adapter that might do the trick.

Thanks in advance!