Capacitors in switching power supplies play crucial roles in filtering, energy storage, and voltage regulation, and bulging is a common failure mode caused by factors such as overvoltage, high temperature, or aging. Replacing bulging capacitors correctly is essential to restore the power supply's functionality and prevent further damage. The first step is to prepare the necessary tools and materials, including a soldering iron (preferably with adjustable temperature, set to 300-350°C), solder wire (with a low melting point, such as 60/40 tin-lead solder), desoldering pump or desoldering braid, new capacitors with the same specifications (voltage rating, capacitance, and package size), and safety equipment like anti-static gloves and goggles.

Before starting the replacement, disconnect the switching power supply from the mains and discharge any residual voltage in the capacitors. This can be done by connecting a resistor (with a resistance of several thousand ohms and a power rating of at least 1W) across the capacitor terminals for a few seconds. Failure to discharge may result in electric shock or damage to the soldering iron. Next, remove the power supply cover to access the internal circuit board. Locate the bulging capacitors; they are usually easy to identify by their swollen tops, leaking electrolyte, or deformed casings.

Use the soldering iron to heat the solder joints of the capacitor's pins on the circuit board. While heating, use the desoldering pump to suck out the molten solder, or press the desoldering braid onto the solder joint to absorb the solder. Once the solder is removed, gently pull the capacitor out of the circuit board. Be careful not to damage the circuit board traces or nearby components. Before installing the new capacitor, verify its specifications to ensure they match the original one. The voltage rating of the new capacitor should be equal to or higher than that of the original, and the capacitance should be the same (a small deviation of ±10% is usually acceptable). Insert the new capacitor into the circuit board, ensuring the polarity is correct (the positive terminal of the capacitor should align with the positive mark on the circuit board, typically indicated by a "+" symbol or a colored line).

Heat the solder joints with the soldering iron and apply a small amount of solder wire to form a firm and smooth connection. Avoid applying excessive solder, which may cause short circuits between adjacent pins. After soldering, inspect the solder joints for any cold solder (dull, grainy appearance) or solder bridges (unintended connections between pins). Once the replacement is complete, allow the circuit board to cool down for a few minutes, then reinstall the power supply cover. Finally, reconnect the power supply to the mains and test its output voltage and stability using a multimeter. If the output is normal, the replacement is successful; otherwise, check for any mistakes in the soldering or capacitor installation.

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