[Ed in Tx]

They are not always visible. This is where an ESR meter comes in handy. With one, you can easily go through a whole board of capacitors and tell which ones are likely bad. When I was working on one with these types of problems, I would test each electrolytic capacitor with my ESR meter, and those that tested with high ESR I would mark with a felt tipped marker as I went through the board, then replace, which usually restored normal operation.