experts help needed

[ahole-ic]

Test the capacitor with a multi meter. According to the text on it, it should read 160v. It looks as though it just wasn't soldered good enough, so my guess is it would be fine to just solder it back on.
After soldering it, test the amp, and make sure to play something for a little while at moderate to high volume and check for overheating and any funny noises or smells.

If the capacitor ends up being bad for some reason, you can find a replacement fairly easily.

no. You don't test a cap's voltage to make sure it's good. Geez.