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.

Even though this power supply has two additional Y capacitors on its transient filtering stage and two additional X capacitors and one additional ferrite coil after the rectifying bridge, it doesn’t have a MOV, which is essential to cut spikes coming from the power grid.

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Figure 9: Transient filtering stage (part 1).

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Figure 10: Transient filtering stage (part 2).

In the next page we will have a more detailed discussion of the components used in the ZM360B-APS.