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The reason why the power supply board makes abnormal noise
1. Common mode inductance causes abnormal noise from the power supply board
There are two main reasons for the abnormal noise of common mode inductance. One is the distortion of the power grid waveform. For example, there is a construction site nearby, or there are thyristor equipment at home (I have encountered a hotel before because of the use of thyristor switch lamps, dozens of machines will make abnormal noises). Second, the single product is bad, and the inductance dipping paint is insufficient. For the abnormal noise of the power supply board caused by the common mode inductance, there is a simple and direct way to short circuit the common mode inductance. This will not affect the use. Common mode inductance is mainly used to suppress EMC interference, and it has no effect in actual use.
2. The film capacitor after the X capacitor/bridge stack causes abnormal noise from the power supply board
The cause of abnormal noise is the same as the common mode inductance, the power grid is distorted or the single product is bad (the winding is not tight). The processing method is also very simple, directly removed. Will not affect the use.
3. Transformer/inductor causes abnormal noise from the power supply board
There are generally two reasons for transformer/inductance ringing, abnormal operating frequency and poor single product. The abnormal working frequency is mainly caused by the damage of the peripheral components of the IC, such as the chip capacitor rupture; the single product is mainly defective or the paint is insufficient. In case of transformer/inductor ringing, first look at the components for damage. I really can't find a replacement board.
4. Jumper/magnetic beads cause abnormal noise from the power supply board
This is what many people will ignore, because of the periodically changing current in the jumper/bead will also cause abnormal noise. The best way for the abnormal sound of the jumper/magnetic bead is to dispense.
