Welcome to the forum.
Search the forum, it has been up here a couple of times, or download the manual (Silver member), its an exenter or the like that has to be adjusted.
Beosound 3000, BL 4000, BL 8000, BG 2404,BG 5000, BG CD50, Beocord 5000, BM 901, BM 2400, BM 4000, BV S45, BV 3702. There is nothing we cannot do, but a lot of things we don't want to do!!