That would require some experience, yet the most common visual clue would be 'bulging'. There are some ways to measure ESR w/o desoldering but they won't be rel

That would require some experience, yet the most common visual clue would be 'bulging'. There are some ways to measure ESR w/o desoldering but they won't be reliable at all times. Measuring voltages, peak to peak, is a bit more work.