Do you have a proper FM antenna plugged it?

It can make a difference.

I use normal dipol antenna, does 2500 require some special impedance?

Btw, as long as I am disassembling the unit, I am going to order all new drive belts - doors, tape and cd tray. (Tape deck doesnt work at all, and sliding doors sometimes stops halfway - I noticed that motor is spinning over belt which is quite loose).

I have found all 3 belts on ebay for cca 30EUR - is this OK or is there a better or better quality source?

And could you point me to some guides/steps for belt replacements and sliders cleaning? I have already opened up the unit and now am searching around forum how to carry on.

I don't think it needs a special antenna, but most of the times it needs one else the tuner is quite weak.

Where are you located? If in the US just order from B&O authorized service center.

The belts unfortunately take a lot of time to change! Lots of dis-assembly required. Make sure you get high quality belts to ensure you don't have to do this again soon!

Can you get the tape mechanism to engage?

Are you certain ALL fuses are OK? There are I think 3 or 4 of them in the unit. If one goes the unit will still "half work."

I bought complete set of new belts (doors, CD tray and cassette deck) and have done a big service yesterday (took me almost 6hrs).
Beosystem now works like a charm :)

But its a hell of a job and interesting thing happened in a cassette deck:

The belt was not just wrapped around motor but it had also melted in a blob of melted rubber which took more then an hour to clean:

Where did you buy your belts?