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.

This power supply is impeccable, bringing one extra ferrite coil and two extra Y capacitors, on this stage, plus one additional X capacitor after the rectifying bridge and two ferrite beads, one on the main AC cable and another on the cable connecting the transient filtering to the main printed circuit board (on this power supply the transient filtering stage is located on a separated printed circuit board, see Figure 7). On this unit the MOV is installed after the rectifying bridge, a configuration that is typical with units using older projects.

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Figure 7: Transient filtering stage (part 1).

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Figure 8: Transient filtering stage (part 2).

In the next page we will have a more detailed discussion of the components used in the Liberty DXX 500 W.