hi i had a similar problem with my Symphony II the backlight was on but no sound. a few weks later a pop and it went dead. however worse still it started to smoke. i pulled the fuse and have had it checked out and they found 2 x 5p coins had got inside and have now burnt out the whole stereo. I dont have young children so the coins came from the loose change drawer above the stereo. i hope you dont have the same. get the stereo removed and give it a shake, if its loose money you may have saved your stereo.
steveroy
November 2009