Common failures of regulated power supply units
blown fuse
Generally, a blown fuse indicates there is a problem with the internal wiring of the power supply. Since the power supply operates at high voltage and high current, fluctuations and surges in the grid voltage will cause the current in the power supply to increase instantaneously and cause the fuse to blow. The focus should be to check the rectifier diode, high-voltage filter electrolytic capacitor, inverter power switch tube, etc. at the power input end to check whether these components have breakdown, open circuit, damage, etc. If the fuse is indeed blown, you should first check the various components on the circuit board to see if the appearance of these components is burned and whether the electrolyte has overflowed. If the above conditions are not found, use a multimeter to measure whether the switch tube has a breakdown or short circuit. . Special attention should be paid to: when a component is found to be damaged, you must not turn it on directly after replacing it. This may cause the replaced component to be damaged because other high-voltage components are still faulty. All high-voltage components in the above circuit must be inspected once. Only after checking and measuring can the fault of the blown fuse be completely eliminated.
Common faults of regulated power supplies
No DC voltage output or unstable voltage output
If the fuse is intact, there will be no DC voltage output at all levels under load. This situation is mainly caused by the following reasons: open circuit or short circuit in the power supply, failure of the overvoltage and overcurrent protection circuit, auxiliary power supply failure, oscillation circuit not working, overload of the power supply, rectifier diode in the high-frequency rectifier filter circuit Breakdown, filter capacitor leakage, etc. After measuring the secondary components with a multimeter and ruling out the breakdown of the high-frequency rectifier diode and the load short circuit, if the output is zero at this time, it is certain that the control circuit of the power supply is faulty. If there is some voltage output, it means that the front-end circuit is working normally, and the fault lies in the high-frequency rectifier and filter circuit. The high-frequency filter circuit mainly consists of a rectifier diode and a low-voltage filter capacitor to form a DC voltage output. The breakdown of the rectifier diode will cause the circuit to have no voltage output, and the leakage of the filter capacitor will cause unstable output voltage and other faults. Damaged components can be detected by statically measuring the corresponding components with a multimeter.
Poor power load capacity
Poor load capacity of the power supply is a common fault. It usually occurs in old-fashioned or long-working power supplies. The main reason is that the components are aging, the switching tube is unstable, and the heat is not dissipated in time. You should focus on checking whether the Zener diode is hot and leaking, the rectifier diode is damaged, the high-voltage filter capacitor is damaged, etc.
