Did you post the same question at Audio Karma?
Depends on how loud you were playing the music. Have you tested the speakers? Look on the back for a small cover that can be removed- it's been a long time since I looked at one but if it has fuses, they may be outside, where it's easier to get at them. Make sure it's unplugged before removing anything like this.
In order to get UL listing, AFAIK, a device has to have some kind of protection like a fuse or breaker for the power supply, but that doesn't necessarily mean the amp has to have its own. You could have launched a driver/pre-driver, an output pack or something else. Try it with headphones- if it works that way, make sure the speaker selector wasn't moved.