We conducted several tests with this power supply, as described in the article Hardware Secrets Power Supply Test Methodology.
First we tested this power supply with five different load patterns, trying to pull around 20%, 40%, 60%, 80%, and 100% of its labeled maximum capacity (actual percentage used listed under “% Max Load”), watching how the reviewed unit behaved under each load. In the table below we list the load patterns we used and the results for each load.
If you add all the power listed for each test, you may find a different value than what is posted under “Total” below. Since each output can vary slightly (e.g., the +5 V output working at +5.10 V), the actual total amount of power being delivered is slightly different than the calculated value. On the “Total” row we are using the real amount of power being delivered, as measured by our load tester.
+12V1 and +12V2 are the two independent +12V inputs from our load tester and during our tests the +12V1 input was connected to the power supply +12V2 rail and the +12V2 input was connected to the power supply +12V1 rail.
|Input||Test 1||Test 2||Test 3||Test 4||Test 5|
|+12V1||5 A (60 W)||10 A (120 W)||15 A (180 W)||20 A (240 W)||24 A (288 W)|
|+12V2||5 A (60 W)||10 A (120 W)||15 A (180 W)||19 A (228 W)||24 A (288 W)|
|+5V||1 A (5 W)||2 A (10 W)||4 A (20 W)||6 A (30 W)||8 A (40 W)|
|+3.3 V||1 A (3.3 W)||2 A (6.6 W)||4 A (20 W)||6 A (19.8 W)||8 A (26.4 W)|
|+5VSB||1 A (5 W)||1 A (5 W)||1.5 A (7.5 W)||2 A (10 W)||2.5 A (12.5 W)|
|-12 V||0.5 A (6 W)||0.5 A (6 W)||0.5 A (6 W)||0.5 A (6 W)||0.5 A (6 W)|
|Total||142.1 W||272.6 W||400.9 W||539.9 W||662.3 W|
|% Max Load||21.9%||41.9%||61.7%||83.1%||101.9%|
|Room Temp.||45.3° C||45.2° C||46.1° C||48.6° C||48.3° C|
|PSU Temp.||50.7° C||50.6° C||51.1° C||52.9° C||54.9° C|
|Ripple and Noise||Pass||Pass||Pass||Pass||Pass|
|AC Power||177.2 W||324.6 W||476.5 W||652.0 W||843.0 W|
|AC Voltage||114.3 V||113.2 V||112.2 V||110.1 V||107.5 V|
Seventeam ST-650P-AF can really deliver its labeled wattage. The problem, however, is that efficiency was below of what we were expecting. Being an 80 Plus Bronze power supply, we were expecting it to present 82% minimum efficiency at light load (20% load, i.e., 130 W) and full load (i.e., 650 W), but this didn’t happen. The reason is that we test power supplies at a room temperature that is double of used by the 80 Plus certification, and the higher temperature the lower efficiency is. We’ve already explained this in more details in our Can We Trust the 80 Plus Certification? article. Another explanation is the load pattern used by 80 Plus. We emphasize load on the +12 V output, as computers nowadays will pull most of their power from this output, since this is where the CPU and the video cards are connected to.
ST-650P-AF presented a good 84% efficiency when we pulled between 40% and 60% from its labeled capacity (i.e., between 260 W and 390 W), dropping to around 83% when we pulled 80% from its maximum capacity (i.e., 520 W). At light load (20% load, i.e., 130 W) it presented efficiency around 80%, dropping below the 80% mark at full load.
It is important to note that we’ve tested two samples from this power supplies and both achieved identical results.
Voltage regulation was the highlight from ST-650P-AF. All voltages were closer to their nominal values than required, always staying below 3% of their official values (ATX specification allows voltages to be up 5% from their nominal values). This includes the -12 V output, which usually doesn’t like to stay in such tight tolerance.
Noise and ripple levels were below the maximum allowed, as you can see below. All values are peak-to-peak figures and the maximum allowed is 120 mV for the +12 V outputs and 50 mV for the +5 V and +3.3 V outputs.
Now let’s see if we could pull more than 650 W from this unit.