Switching power supply chips, such as PWM (Pulse-Width Modulation) controllers and voltage regulators, are the "brain" of the power supply, and their burnout can render the entire system inoperable. Repairing burned-out chips requires a combination of technical knowledge, careful inspection, and precise operation. The first step is to identify the burned-out chip. Visually inspect the circuit board for signs of chip damage, such as charred marks, melted plastic, or missing pins. In some cases, the chip may not show obvious physical damage, so it is necessary to use a multimeter to measure the voltage at the chip's key pins. For example, check the input voltage pin (VCC) to see if it receives the correct voltage; if there is no voltage or the voltage is too low, it may indicate a problem with the power supply to the chip or a burned-out internal circuit.

Before replacing the burned-out chip, it is important to identify the root cause of the burnout to prevent the new chip from failing again. Common causes include overvoltage input, short circuits in the output circuit, faulty components (such as diodes or transistors) connected to the chip, or poor heat dissipation. Use a multimeter to check the output circuit for short circuits by measuring the resistance between the output terminals; a low resistance reading indicates a short circuit, which may be caused by a faulty rectifier diode or filter capacitor. Additionally, check the components connected to the chip's control pins, such as resistors and capacitors, to ensure they are not open or short-circuited.

Once the root cause is identified and resolved, proceed to replace the chip. For through-hole chips, use a soldering iron and desoldering pump to remove the old chip, similar to the capacitor replacement process. For surface-mount chips (SMDs), which have smaller pins and are mounted directly on the circuit board surface, a hot air rework station is more suitable. Set the hot air temperature to 250-300°C and the air flow to a moderate level. Hold the hot air nozzle above the chip, moving it in a circular motion to evenly heat the pins. Once the solder melts, use tweezers to carefully remove the chip from the circuit board. Clean the solder pads on the circuit board using a desoldering braid to remove any residual solder, ensuring the pads are flat and clean.

Before installing the new chip, verify its model number to ensure it is identical to the original one (compatible substitutes may be used if the exact model is unavailable, but their electrical parameters must match). For surface-mount chips, apply a small amount of solder paste to the solder pads on the circuit board (using a syringe or a small spatula). Place the new chip onto the solder pads, aligning the pins with the pads (use a magnifying glass if necessary to ensure accurate alignment). Use the hot air rework station again to heat the chip, melting the solder paste and forming a secure connection between the chip's pins and the circuit board. For through-hole chips, insert the pins into the holes on the circuit board and solder them as described earlier.

After installing the new chip, perform a comprehensive test. Reconnect the power supply to the mains (use a variable power supply for initial testing to avoid overvoltage) and measure the voltage at the chip's key pins and the power supply's output terminals. Check for any abnormal heating of the chip or other components (use a thermal imaging camera or a hand-held thermometer). If the output voltage is stable and within the specified range, and there are no signs of overheating or other faults, the repair is successful. If problems persist, recheck the soldering, the root cause analysis, and the compatibility of the new chip.

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