Amp Pop and Hum, fried?
 

Today I was playing, and my amp popped really loudly and started to hum. The cable is fine, and the amp still hums even without anything plugged in. When I turn it on, it hums and my pre-amp clip LED light is on. None of the knobs affect the hum, and there's no sound from the bass when plugged in. Volume doesn't affect the noise of the hum, although the tweeter off/headphone/full range rocker switch works. It does make a really loud popping noise when I plug and unplug the cord though. The fuse is okay, the power cable is 3-pronged, in good condition and everything is properly grounded. It's an older Workingman's SWR 15 combo that I bought used from guitar center 2 or 3 years and this is the first time I've ever had any issues with it. Does any body have an idea what's wrong?

Here are pictures of the amp, so you can see the model.

unplug the speaker and check the output for dc. Don't try turning it on again with a speaker attached until you've checked this

Sometimes, it's not that hard to open it up and see what's wrong.
Unplugged, of course. ;)
Look for burn marks, leaking or bulging capacitors, etc.
Capacitors and resistors are pretty easy to replace, though you do need to take care to drain capacitors before messing with them. They hold a bit of a charge for a while.
You can find out about this stuff online.
I mean, I'm not an expert, so proceed at your own risk, but I've so far saved a pair of studio monitors and a Peavey Classic 20 by swapping out a single, super cheap capacitor.