Our family just purchased a 1985 Mercedes and i dont think i can turn the key back to just put the radio on like one can in other cars.

Is that right or am i missing it completely?

is it a diesel?
if yes, you have to turn it until the ignition light turns on. instead of starting it, you just keep the key in position.
normally the radio should work now.

at least, it worked for me before I bought a new radio -
I installed my radio/cd with permanent current supply. It's connected with an amplifier which is directly connected with the battery.
so I can listen to it even without a key.

cu

yeah its diesel, ill try that

if it is a diesel you must be sure that the glo plugs are not lit while you listen to the radio, if they are this will shorten their life drastickly