As we have mentioned in other articles and reviews, the first place we look when opening a power supply for a hint about its quality, is its filtering stage. The recommended components for this stage are two ferrite coils, two ceramic capacitors (Y capacitors, usually blue), one metalized polyester capacitor (X capacitor), and one MOV (Metal-Oxide Varistor). Very low-end power supplies use fewer components, usually removing the MOV and the first coil. 

In this power supply, this stage has four Y capacitors and one ferrite coil more than required (plus an X capacitor after the rectifying bridges), however it doesn’t have an MOV, which is the component in charge of removing spikes coming from the power grid.

click to enlarge
Figure 8: Transient filtering stage (part 1)

click to enlarge
Figure 9: Transient filtering stage (part 2)