Speedometer stopped working - 1992 400E

[parnelltk]

I have a 1992 Mercedes 400E and the Speedometer suddenly stopped working last week. I am trying to get some information and tips for diagnosing and repairing the problem. I understand that this model does not have a speedometer cable but rather has a transmitter sender unit? Are there any fuses that need to be checked? Where is the transmitter located? Is there anything to test or repair or do I just need to replace the transmitter? Other suggestions?
Thanks,
Kim