There may be a fuse on the amp plate on the back, if it is good then the amp is probably bad. The KSW line was not one of Klipsch's finer moments. KSW = Krappy Sub Woofer
I bought a KSW-15 brand spanking new from an authorized dealer it had a list price of $750 and I got it for $500 and it was just junk. The cheap carboard port came loose and I had to silicone it back in place, the trim ring on the woofer fell off and I had to silicone it as well. It would shut off various times during movies since it wanted to see a signal to stay on in "Auto" mode and I did not want to leave it "always on"
I bought a Velodyne and it was not even a contest, great thing was I kept it pristine with all the packing and got good money for it when I got rid of it. I sure do not miss it at all. The only Klipsch subs that I would consider would be the THX Ultra sub duo, the RSW models, and perhaps the new RT line.