I have a pair of BL 4000, had them connected directly to my wall power jack, one of them sometimes showed green light, but no sound.
I brought it to B&O Mexico city, no solution, but a fine cross scratched on the top of the fine polished aluminium.
Sometime later I connected all my speakers to a nobreak powersupply, and after that no problems. We have a lot of brown and black outs here in our area, sometimes the power is down to 85-90 volts, the funny thing is that only one speaker failed, I also had two BL 8000 connected at the same time, but no problems.
So check your power, or try with a nobreak
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!!