As we mentioned in other articles, 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, which is essential for cutting spikes coming from the power grid, and the first coil.

This power supply from Corsair uses one MOV, four ceramic capacitors, one metalized polyester capacitors and three ferrite coils, plus a ferrite bead on the main power cord, so it has one coil more than required.

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Figure 10: Transient filtering stage (part 1).

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Figure 11: Transient filtering stage (part 2).