W220 COMAND Not Working

Hi folks, I've recently bought an early W220 but the Stereo/Nav/CD/Phone isn't working. It is the early version of COMAND, so far as I can tell the fuses are OK however the fuse diagrams are missing.

Head unit/phone/nav - not working at all.
CD changer - eject button tries to eject CD cassette but appears broken. However this suggests there is at least power going to the unit.

I pulled the head unit from the dash and found that there is power on both the switched feed and permanent feed. Therefore I'd guess the problem is in the head unit itself?

Any help would be much appreciated, I'd very much like to have the system working!

 

New head unit fitted, which works well.

Unfortunately it's now revealed the next issue, which is no sound. The Bose amp and CD changer are damp so I can only guess these have both failed. There is power to both but nothing coming out of them.

 

Possible fibre optic circuit failure, try removing devices from the ring with af/o connector till it works.