I have a PSW140 subwoofer that is probably about 5 years old and all of a sudden decided to stop working. I unscrewed the back of the speaker box and the fuse was blown. I went to Radio shack and they sold me fuses that they said would work for the speaker. I put the fuse in the speaker and it makes a humming noise for about 2-5 seconds and blows the fuse. Any suggestion on how to fix the speaker would be appreciated.