Ok, thanks again
I went into the servicemenu, changed slot assignment to AV and now the computer image shows up on one of the two dvi choices, dvd(dvi) and dvd2(dvi) on the AV connection section.
I changed the scartplug with its audio-rca cables connected and instantly I got regular stereo sound again.
I changed the digital cable to spdif 1 and no sound
I changed it back just to be sure, no sound.
Maybe there is something with that I need to output surround sound ? I tried to play a dvd on mac dvd-player program, no sound
Maybe the converter is broken. I have this one currently
http://www.national-tech.com/specs/toslink-to-digital-coax/10tr-08300.htm