Kenwood 1060vr - help please!

I'm having a problem with my amp. It mysteriously lost it's A-speaker use and surrounds/center. The speaker input for fronts(a-channel) and center is banana type although i'm using regular speaker wire. i've been forced to use the b-channel in stereo only. i've been searching the net but have come up short finding out what the problem is, i was hoping it was a simple fuse problem but i'm doubtful. i dont want to take it to a shop because of the amps age/value. any info would be greatly appreciated.