Method for detecting inverter IC short circuit: The inverter uses the method of disconnecting the load circuit one by one to check which load circuit the inverter short circuit fault is in, or after a power outage, measure the output end of each power supply to see if there is a decrease in resistance or short circuit. Measuring both ends of the +5V power supply, a small resistance value of 7.8Ω is presented, while the normal circuit resistance is about hundreds of Ω. It is judged that the +5V load circuit has a short circuit. After disconnecting the +5V load circuit, the switching power supply has a stable output, indicating that the fault is in the +5V load circuit.
+5V power supply goes from the cable terminal to the CPU motherboard, supplying CPU chips and peripheral circuits. The circuit range is relatively wide. There are many integrated circuits with +5V power supply on the CPU motherboard, up to more than 20 pieces. To check the short circuit fault by conventional elimination method, the +5V power supply pin of each IC circuit must be picked up, and the resistance value of the power output end must be detected. When the power supply pin of a certain IC is picked up, the small resistance value of 7.8Ω at the power output end becomes a normal resistance value, indicating that the IC has a short circuit fault. Of course, the power supply pin of the IC is measured and the resistance value of its power supply pin is detected in the same way.
However, we cannot predict how many ICs need to be picked up before the faulty IC can be found. The "sophistication" of CPU motherboard component welding is close to that of mobile phone circuit boards. IC circuits are all chip components. It is not even an exaggeration to say that the copper foil strips of IC pins are thinner than hair.
Therefore, if you are not careful and pick off the copper foil strips, it will be difficult to connect them, but picking them one by one is too slow. Since the switching power supply has limited load capacity, it will trigger overcurrent protection when connected to a faulty circuit, causing the switching power supply to stop outputting. Therefore, an external +5V power supply with a larger capacity is used, and a 5Ω5W current-limiting resistor is connected in series to the CPU motherboard. After powering on for a few minutes, touch the IC chip on the CPU motherboard with your hand. If any chip is hot and has an abnormal temperature rise, that IC is broken.