The nice thing about caps is often they physically show signs of distress. The tops will bulge up. In my experience as a computer tech you can often see a physically bad cap.
Example, a freind was having problems with his computer booting and then shutting down and not rebooting. Popped the side off, blew 5 years of dust out with the compressor. Wiped said dust off the front of my land rover.(you can skip this step if you dont have a rover, or dont point the dust at it) Booted it up and saw the caps on the mother board all had domed tops and the little croses at the top were split. They also became too hot to touch after about 30 seconds.(power anything off and know what your touching first, trust me I used to fix Pc monitors) He's getting a new mother board and to be safe powersupply.(often bad/weak ps will damage these type things)
So what im saying is, if you are qualified. Unplug your amp let it sit for abit(overnite) so the circuits are all discharged. Remove the chasis and physically inspect everything. You may see burnt/cracked components, or caps with the tops bubbled or poped. When you can see phsyical signs of distress on a component you can put down the testing equipment and replace it.