amp question...what the hell is goin on????

I have a question to anyone who knows a thing or two about amps. My band played a wedding reception yesterday and right as we were about to begin, my amp wasn't working. The power indicator light was on everything was plugged in correctly, but didn't get any sound. I unplugged my chord from my guitar and touched the end and still no sound or hum, nothing! Out of frustration and embarassment, i hit the top of my amp and wouldn't ya know the damn thing made noise!! I have never had a problem like this before and unfortunately it happened a few more times after that as well. I know the amp is a  little older, but just recently replaced the fuse and I believe the contact, not sure what it is called but it was a small piece that was relatively cheap to replace much like the fuse was. I haven't had this problem before and was wondering if it was a sign of worse thing's to come or maybe a power supply issue or if I  just need to replace my power chord on the amp. If anyone knows what the problem might be a response would be most appreciated!! thank you!