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.

The metal component that looks like a regular power socket in Figure 7 is in fact a complete filtering circuit, with all required components listed above inside it, but the MOV.

ASUS U-75HA also has three ferrite coils, two X capacitors and four Y capacitors more than the minimum required, but it doesn’t come with a MOV (component in charge of removing spikes coming from the power grid), which is a sin. We expected it to have one, since it carries the name ASUS.

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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 ASUS U-75HA 750 W.