everything works except speakers, i fried the head unit whiile installing?

When I was installing my stereo I had the red wire from the battery hooked up to the stereo while the car was running and the head unit shorted out. I think it's an alpine with a built in usb port. really nice, got itfromcircuit city and couldn't return it. Everything works except for the speakers. I installed a new one, but don't know how to fix the old one.
The faceplate lights up, and I can see the volume playing-cd's play, but the speakers do not work. Is there an easy way to fix it? maybe a little soldering and it can be brand new?