My 1993 Mercedes 300D Turbo radio/cassette player suddenly stopped working and the display says "TEF". I have tried turning it off and on, but still get no sound and the TEF display. none of the buttons work. Can anyone tell me what this means??

Just fishin' here for something you can try. The radio on my 1988 W124 is different from the one in yours, and I don't ever get TEF on the digital display. However, once in a blue moon the radio will lock up and lose all functionality. Greeking characters fill the display, and the radio antenna won't retract when the ignition key is turned off. When that happens, I've tried removing the radio fuse, to no effect. The only thing that's worked for me is to remove the negative battery cable for a couple of minutes. When reattached, the antenna immediately retracts and the radio is fine. It's possible that removing power will cause a resetting of some ECUs, but that's never been an issue with my car. Maybe that'll work for you.

Edit: Have you read the audio system brochure or owner's manual that came with your car for any guidance as to the meaning of codes like TEC?

Try disconnecting the 5 pin plug on the back of your radio. That should do it. You don't need it to be connected for the radio to work.

Cleeve Morrison
La Jolla Audio Repair
www.lajollaaudiorepair.com