On the pictures below you can have an overall look from our generic 500 W unit. One difference between this unit and “branded” units we could see right away was the gauge of the wires used on the AC connection (18 AWG) and on the 110/220 V switch (20 AWG), way thinner than the ones used on good power supplies. The thicker the wire, the more current it can transport.

Other visible differences include the size of the printed circuit board (smaller on generic units), the size of the main transformer (smaller on generic units, meaning less current/power it can deliver), and the number of available components (fewer components on generic units).

click to enlarge
Figure 4: Overall look.

click to enlarge
Figure 5: Overall look.

click to enlarge
Figure 6: Overall look.

Power supply manufacturers reduce the cost of the power supply by using cheaper components and simply removing components. On the primary you can see that practically all components from the transient filtering stage are missing and on the secondary less capacitors and coils are used on the filtering stage.

The recommend components for the transient filtering stage are two ferrite coils, two ceramic capacitors (Y capacitors, usually blue), one metalized polyester capacitor (X capacitor) and one MOV (Metal-Oxide Varistor). This generic 500 W power supply has only the two Y capacitors, all other components were removed. If you pay attention on the printed circuit board you will notice that the places for these other components exist and they are probably used on a “upgraded” versions of this power supply (ZNR1 and ZNR2 for the MOV’s, CX1 for the X capacitor and LF1 for the ferrite coil, see Figure 7).

click to enlarge
Figure 7: Location of the transient filtering stage – this power supply has only two Y capacitors here.

In the next page we will have a more detailed discussion of the components used in the our generic 500 W unit.