Is this a relatively new amp? Say, within the last eight years or so? I hadn't heard of any audio equipment being impacted, but I have had other consumer electronics die from bad capacitors. Wikipedia calls it "Capacitor plague".

A conventional multimeter might not read well. I think you need one of those "True RMS" ones to get accurate readings with AC signals. I'm not sure, though. I'm the wrong kind of techie.

Finally, I have heard a tick-tick-tick sound coming from a car before, that sounded a lot like a CD skipping. We were at about 13,000ft, and an electrical storm came over. We were bleeding static out of the air through the antennas. Each 'tick' was a spark jumping to ground.