Radio Don't work

[grubster@megsinet.net (Martin Gruby)]

yesterday when I woke up, got ready for school.  I got in my 1988 Audi 80
quattro and turned the key.. Practically didn't make a noise.  That battery
went bad.  I got a brand new interstate for 52 bucks.  It works fine now.
Tested the battery and it was bad.

Now, I get in my car and turn on the radio.. nothing. It just says "SAF E"
On the screen like what would happen if the radio is taken out of the car or
something. What do I do, and why did this happen??  I think with a Mercedes
you have to leave the radio on for like 12 hours to get it to reset or
something.  Is that what I do here. If not, what do I do. It's boring to
drive fast with no driving music!! 

Any help appreciated.  I have the normal AM/FM cassete player that comes
with this car. '88 80 quattro.