renault espasse mk3 head unit problem

I have changed battery on my espasse and found the fuse had blow eventually changed both fuses the radio can be tuned in cd player shows disc but cannot hear any thing on speakers display keeps going too phone the code cannot be found by Renault dealers as Renault label is missing from head unit can hear a slight hiss on right speakers but nothing music wise they have used my logbook to search .no luck has anyone come across this problem .:(