Batboard

a friend of mine hooked up positive and negative backwards is there a fuse in the radio that i can change.

Yep, they can be in a couple of different places, depending on your board version. Here's a link with good pictures:

http://www.repeater-builder.com/maxtrac ... mpers.html

It's labeled "ign ctrl" in the pics. Hopefully nothing else blew.

Todd

There's a diode or transient protector in the PA section connected right across the power jack, usually that's what goes if power is connected backwards.
It will usually short out, blowing the external fuse (if one was used), or sometimes it will open circuit, in which case further damage to other components like the PA transistors and audio PA chip can occur.