Result Summary

The FOCUS GX ATX 3.0 850 W completed all our tests without issues, including the 110 % overload test in increased ambient temperature. Just as promised in the specifications, the fan stood still until we hit 30 % of the PSU's maximum load. While the ramp up was not overly smooth, starting at around 700 RPM, the noise levels were kept well controlled, even up to the final tests with the fan never reaching its 2000 RPM limit.



The efficiency of the Seasonic FOCUS GX ATX 3.0 850 W is well within the expected 80 Plus Gold range, with peak efficiency of almost 92.3 % in our test setup. At the beginning we are at a slow start with 5% load efficiency reaching just over 82 %, while typically we would be expecting a number above 85 %. For the rest of the tests, the only time the efficiency dips below 89 % is at 110 % of the PSU's rated capacity. Overall, no surprises and a very solid performance.

Voltage Regulation

When it comes to voltage regulation, the FOCUS GX performs really well. The +12 V rail is controlled very well, reaching a maximum deviation of only 1.25 % in its normal operating range. But besides that, both minor rails also perform exceptionally well with just over 1.5 % deviation for the normal operating range.

Ripple

Ideally you want the DC voltage delivered by your power supply to be a completely flat line when looking through an oscilloscope. However, due to the switching nature of ATX power supplies and the less than ideal real world behavior of all the components involved, we get very small fluctuations in output voltage, known as ripple and noise. The ATX spec allows a ripple of up to 120 mV for the +12 V rail and 50 mV for the minor rails.


Ripple is controlled very well, even at high loads. No unusual patterns were observed during testing. Below you can find the image of ripple at 110% of the PSU load.

Short Circuit Protection

Short circuit protection is one of the most fundamental and important protections for a power supply. If a short circuit is detected on any rails, the PSU should turn off and prevent damage to itself and other components.


SCP worked as expected with the unit.