Audio Systems: My Becker Gran Prix Radio wont work, mercedes 380sl, power antenna

Question
I have a 84 Mercedes 380sl with a Becker Gran Prix radio. Today I was driving around and it was working without a problem. I stopped for 5 minutes at a store, came out, started the car and the radio doesn't work. Instead of music I get a loud thumping noise from the speakers and the radio has no characters on the radio station display and I can't turn the radio off ( to get rid of that thumping noise). In addition, the power antenna won't go up. I tried pulling and replacing the fuse but that didn't solve the problem other than the thumping noise stopped when the fuse was pulled. Any idea what the problem is?

Also, I hear that these radio have an anti-theft feature that requires either a code or possibly going to a Mercedes dealership for resetting with a special reset key.  Do you know which one it is?

Thanks

Answer
Dave,

 i'm unsure if your sound system has a factory amplifier or not but this could also be a problem point , but as for now it sounds like your radio has a short in it , loose wire or connection or in the harness itself, my best advice is stop by a good mobile audio repair store and let them do some tests and really get in and check out to find your problem, since they have the tools to check it hands on i'am at limits with what i can do over email,  but i would say you will be replacing the radio unit most likly... hope this helps you out sorry i cant do more if you need anything else let me know

thanks

CM