[Riche]

Try removing the adapter, changing the fuse and conecting the wires directly to the battery... If the fuse blows then, the radio is screwed. If the radio is good, I would get a test light and figure out which wire does what, another old trick to finding the speaker wires is to take a 9 volt batery(with the key off) and touch 2 wires at a time... when you get 2 speaker wires the speaker will pop. It will not hurt the speaker as long as you do not leave the battery connected!!!
hope this helps.