Simple. There is leakage outside the electrolytic capacitor, the pins of the electrolytic capacitor are easy to loosen, and the top of the electrolytic capacitor is obviously raised. Electrolytic capacitance is a kind of capacitance, the metal foil is the positive electrode (aluminum or tantalum), and the oxide film (aluminum oxide or tantalum pentoxide) of the metal close to the positive electrode is the dielectric.