As we mentioned on other articles and reviews, the first place we like to take a look when opening a power supply to have a hint about its quality is its filtering stage. The recommend 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 than that, usually removing the MOV and the first coil.

The transient filtering stage from this power supply is flawless, providing two Y capacitors, one ferrite coil and one X capacitor more than required, plus one X capacitor after the rectifying bridge. The MOV is located behind the fuse on Figure 8 and that’s why we can’t see it on this picture.

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Figure 7: Transient filtering stage (part 1).

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Figure 8: Transient filtering stage (part 2).

Now let’s have a more detailed discussion on the components used on Seventeam ST-620PAF.