Testing

The massive 140mm crystal clear fan is made by Yate Loon. The internals of the unit are similar to the 4775-400 which we reviewed a while back, but not the identical. There are larger heatsinks, which in combination with the 140mm fan will be more than enough to keep the unit cool under stress.

To test the power supply unit, we will use power resistors which are nothing more than normal resistors but capable of consuming a good amount of power. The amount of power depends on the resistance and capability of the resistor, and can be easily calculated by Ohm’s law (Amperes = Voltage / Resistance, Power = Voltage * Amperage).

For example a 1Ohm resistor attached to the 3.3V line will allow 3.3A through it and consume about 10W of power. When adding two of these resistors in parallel, you double the power consumption and allow 20W to be consumed as you halve the resistance this way. Adding more will increase the power consumption. Of course that is not entirely accurate on paper as the fault tolerance of these resistors is high and almost none are exact to their resistance specifications, but after using them we could calculate how much power each bunch of them would consume accurately. This way we can add fake load to any power supply unit, and on any power line we wish with good accuracy.

For testing the NorthQ 4775-500S, taking into account its design and power specifications, we took the following steps:

Total Load	3.3V Load	5V Load	12V-1 Load	12V-2 Load
33% (~170W)	18A (60W)	8A (40W)	3A (36W)	3A (36W)
50% (~250W)	18A (60W)	18A (90W)	4A (48W)	5A (60W)
75% (~380W)	18A (60W)	18A (90W)	10A (120W)	9A (108W)
100% (~470W)	25A (83W)	18A (90W)	12A (144W)	13A (156W)

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The room temperature when the test took place was 30 Celsius degrees, a warm summer day. Under these conditions, the 4775-500S could work continuously at its specified full load, but no more, as the unit would shut down after a few moments. A few small resistors are always attached at the negative and VSB lines, creating a small continuous load on them. The unit proves to be considerably stable, even though the 12V lines fall slightly below specification at high loads, but not nearly low enough to cause a problem.