So um... Nobody knows? Comon, guys. I searched all over the forum and found some messages related to my problem.
So basically there's a fuse inside the D3, that probably went out in my head unit. The complicated fix is to disassemble the whole unit, locate and replace fuses. The simple fix is to connect RCA shields (outer wires of all RCA's) to the ground.
Just like on that picture:
BUT IT IS DANGEROUS, BECAUSE IT CAN FRY THE UNIT at some point.
People also describe some generator whine in their speakers, I don't have any whine. The sound is clear and sharp, but not coming out of