My guages don't work on the dash-help!

I have a 93 Mercedes 300E 6-cylinder gas wagon. This morning when I started the car there was a loud buzz inside of the car and my guages i.e. gas, temperature, oil pressure and tackometer were not working. The buzz is intermitent and seems to be coming from in front of the firewall behind the fuze box. What do you think the problem nay be? Thanks.