"Unknown Disc"-Problem on LINN Unidisk SC

[Lefreak]

Hi,
I got a Unidisc SC which had problems with reading any discs (sometimes it managed to play CDs). Now I got myself a replacement laser (Sony KHM-230AAA). After installing it, the SC reads CD's again, but no DVD-Video/Audio or (Hybrid-) SACD. Do I have to re-initiate the SC so that it remembers how to read other discs than CD's or does the machine have another problem? Unfortunately LINN no longer services their discplayers.

best regards
Thierry