i had a harman kardon system on my 2006 r class as it broke i bought a ntg2.5 hdd dvd comand. problem is every thing is working but no sound from the speakers, any body can help me to resolve please
The HK amp in NTG2 (what you had before) and NTG2.5 is different. However, on some ML/GL/R class the old amp does work - and I haven't yet worked out which ones do and dont.
The first thing you must do is ensure it is the only thing on the fibre optic network - i.e bypass and phone controller, CDC, voice recognition controller, etc
Then you must have the NTG2.5 coded to use an external amplifier.
Then see if it works. If it doesn't you have to put the new NTG2.5 amplifier in and subwoofer amplifier also, and a new speaker wiring loom (which can be spliced to the current one for most of the wiring)