Just finished repairing my new(used) amplifier! For those who don't remember, I bought the thing, opened it up, and found a capacitor dangling from one lead
First, I cut a hole in the back of the amplifier's 3/8-1/2"-thick aluminum body to access the rear of the circuit board. Then I de-soldered the remaining lead because it looked weak. Next I soldered single-wire copper extensions on to the capacitor's two leads and tucked them through the holes in the PCB so that they stuck out a good bit on the back side. I held the soldering iron against the copper wire but away from the PCB, surrounding the wire in a bubble of solder to conduct heat better, and then I stuck the solder against the wire right where it stuck out of the circuit board to secure it.
Lastly, I snipped the excess wire.
It was a lot easier than I expected, once I finished cutting the stupidly thick metal. Burned out the brushes on my Dremel 400 and got a replacement B&D rotary tool which I feel is much stronger, not to mention it's compatible with all of my dremel accessories.