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 flawless on this stage, providing two extra Y capacitors and one extra ferrite coil, plus an extra X capacitor after the rectification bridge. On this power supply the MOV is located after the rectifying bridge and not before, as usual.

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Figure 8: Transient filtering stage (part 1).

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Figure 9: Transient filtering stage (part 2).

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