Electrolytic capacitor

An electrolytic capacitor is a small aluminum can that stores electrical charge and lets it out again, smoothing bumps in a voltage. It packs far more storage into its size than most other capacitors, which is why power supplies are dotted with them.

Inside are two long strips of aluminum foil. The anode foil is etched until its surface is a maze of tiny pits, multiplying its area many times. It is then charged in a chemical bath, which grows a layer of aluminum oxide only nanometers thick on every surface. That oxide is the insulator that holds the charge, and its thinness is the secret of the high capacity. Strips of paper separate the anode from a second foil, and the stack is rolled up like a carpet. The roll is soaked in an electrolyte based mostly on ethylene glycol, sealed in an aluminum can with a rubber plug, and covered with a printed PVC sleeve.

On the power supply board, large ones store energy and smooth the voltage. Their liquid slowly dries out, faster when hot, so bulging or leaking capacitors are a common cause of TV failures.