Test Setup

All measurements were performed using two Chroma 6314A mainframes equipped with the following electronic loads: six 63123A [350 W each], one 63102A [100 W x2], and one 63101A [200 W]. The aforementioned equipment is able to deliver 2500 W of load, and all loads are controlled by a custom-made software. We also used a Picoscope 3424 oscilloscope, a Picotech TC-08 thermocouple data logger, a Fluke 175 multimeter, and a Yokogawa WT210 power meter. We also included a wooden box, which, along with some heating elements, was used as a hot box. Finally, we had at our disposal four more oscilloscopes (Rigol 1052E and VS5042, Stingray DS1M12, and a second Picoscope 3424), and a CEM DT-8852 sound level meter. You will find more details about our equipment and the review methodology we follow in this article. Finally, we conduct all of our tests at 40-45°C ambient in order to simulate with higher accuracy the environment seen inside a typical system, with 40-45°C being derived from a standard ambient assumption of 23°C and 17-22°C being added for the typical temperature rise within a system.

Primary Rails Voltage Regulation

The following charts show the voltage values of the main rails over a range from 60W to the maximum specified load, and the deviation (in percent) for the same load range.

5VSB Regulation

The following chart shows how the 5VSB rail deals with the load we throw at it.

Hold-up Time

The hold-up time is a very important characteristic of a PSU and represents the amount of time, usually measured in milliseconds, that a PSU can maintain output regulations as defined by the ATX spec without input power. In other words, it is the amount of time that the system can continue to run without shutting down or rebooting during a power interruption. The ATX spec sets the minimum hold-up time to 16 ms with the maximum continuous output load. In the following screenshot, the blue line is the mains signal and the yellow line is the "Power Good" signal. The latter is de-asserted to a low state when any of the +12V, 5V, or 3.3V output voltages fall below the undervoltage threshold, or after the mains power has been removed for a sufficiently long time to guarantee that the PSU cannot operate anymore.



The hold-up time is very low and currently one of the lowest we have ever measured (Corsair's CX750 easily wins the fail award in this test). The production cost reduction unfortunately led to a smaller hold-up cap that cannot cope with the full power of the unit once input power is removed.

Inrush Current

Inrush current or switch-on surge refers to the maximum, instantaneous input-current drawn by an electrical device when first turned on. Because of the charging current of the APFC capacitor(s), PSUs produce large inrush-current right as they are turned on. Large inrush current can cause the tripping of circuit breakers and fuses and may also damage switches, relays, and bridge rectifiers; as a result, the lower the inrush current of a PSU right as they are turned on, the better.



The hold-up cap is small (aka has a low capacity), but the inrush current it creates is high enough, which leads me to the conclusion that the corresponding thermistor doesn't have the right resistance to achieve an inrush current close to or below 30 A, but a reading below 40 A is not bad at all for a PSU with such a capacity.

Voltage Regulation and Efficiency Measurements

The first set of tests revealed the stability of the voltage rails and the efficiency of the ETL650AWT. The applied load was equal to (approximately) 20%, 40%, 50%, 60%, 80%, 100%, and 110% of the maximum load that the PSU can handle. We conducted two additional tests. In the first test, we stressed the two minor rails (5V and 3.3V) with a high load while the load at +12V was only 2 A. In the second test, we dialed the maximum load that the +12V rail could handle while the load on the minor rails was minimal.


Efficiency with up to a 60% load is high enough, especially for a Bronze unit. Only afterwards does it start to decrease noticeably. However, we pushed the unit really hard compared to PSUs with a higher efficiency. Its own heat contribution quickly made temperatures inside our hot box shoot up, with, of course, the help of the heating elements the latter offers. The ambient reached 47°C instead of the usual 45°C during the full load test.

Voltage regulation on all major rails is within 3%, but the voltage of the 12V rail dropped quite low, especially during the full load and 110% of maximum-rated-capacity tests. We would like to see values closer to the nominal voltage readings on this rail. Also, the group regulation scheme is responsible for the horrible performance on both cross-load tests, where the +12V rail failed to keep its voltage within the specified limits. Finally, the fan spun at high RPMs in almost all tests. The fan, as you can see, registered its highest rotational speed during the CL1 test. The fan was fed by +12V during this test, which made the rail go crazy. The rail dropped dead low during the CL2 test despite a high load and ambient temperatures above 43°C, which, unlike the RPMs we registered during the 80-110% load tests, kept the fan below 2200 RPM.

The low voltage readings that the +12V rail registered with high loads and the unit's poor performance during the cross-load tests spoiled the general picture, reminding us of older designs/platforms that have no place in a contemporary systems.