PC Power & Cooling Silencer Mk II 750 W Power Supply Review
Load Tests
Contents
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.
The +12VA and +12VB inputs listed below are the two +12 V independent inputs from our load tester. Since the reviewed unit has a single +12 V rail, both inputs were connected to the power supply single +12 V rail (+12VB was connected to the power supply EPS12V connector and all other cables were connected to the load tester +12VA input).
| Input | Test 1 | Test 2 | Test 3 | Test 4 | Test 5 |
| +12VA | 5 A (60 W) | 11 A (132 W) | 16 A (192 W) | 22 A (264 W) | 27 A (324 W) |
| +12VB | 5 A (60 W) | 10 A (120 W) | 16 A (192 W) | 21 A (252 W) | 27 A (324 W) |
| +5V | 2 A (10 W) | 4 A (20 W) | 6 A (30 W) | 8 A (40 W) | 10 A (50 W) |
| +3.3 V | 2 A (6.6 W) | 4 A (13.2 W) | 6 A (19.8 W) | 8 A (26.4 W) | 10 A (33 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 | 150.1 W | 302.4 W | 453.9 W | 602.5 W | 750.4 W |
| % Max Load | 20.0% | 40.3% | 60.5% | 80.3% | 100.1% |
| Room Temp. | 47.1° C | 47.6° C | 48.4° C | 46.8° C | 47.5° C |
| PSU Temp. | 46.3° C | 46.8° C | 47.6° C | 46.7° C | 47.3° C |
| Voltage Stability | Pass | Pass | Pass | Pass | Pass |
| Ripple and Noise | Pass | Pass | Pass | Pass | Fail on -12 V |
| AC Power | 174.0 W | 342.7 W | 517.7 W | 699.0 W | 891.0 W |
| Efficiency | 86.3% | 88.2% | 87.7% | 86.2% | 84.2% |
| AC Voltage | 111.1 V | 109.4 V | 105.7 V | 103.6 V | 101.6 V |
| Power Factor | 0.949 | 0.981 | 0.989 | 0.993 | 0.995 |
| Final Result | Pass | Pass | Pass | Pass | Pass |
The PC Power & Cooling Silencer Mk II 750 W can really deliver its labeled wattage at high temperatures.
Efficiency was very high at all times, peaking at 88.2%. At full load, however, we saw efficiency at 84.2%, which is a tiny bit below what is promised by 80 Plus Silver certification (85% minimum at 20% and 100% loads; 88% minimum at 50% load). This normally happens in our tests, since, for obtaining the 80 Plus certification, power supplies are tested at a room temperature of only 23° C, which is too low. We test power supplies between 45° C and 50° C and efficiency drops with temperature. Therefore we consider our tests more realistic than the ones conducted by 80 Plus.
Voltage stability was another highlight from the PC Power & Cooling Silencer Mk II 750 W, with all voltages inside 3% of their nominal values (i.e., voltages were closer to their nominal value than needed, as ATX spec allows voltages to be up to 5% from their nominal values, 10% for -12 V). This includes the -12 V output, which usually doesn’t like to stay within a tolerance this tight. The only exception was +3.3 V during test five, which was still inside the proper range.
And finally we have noise and ripple, which were always at very good levels (i.e., low). Below you can see the results for test number five. As we always point out, the limits are 120 mV for +12 V and -12 V outputs, and 50 mV for +5 V and +3.3 V outputs and all numbers are peak-to-peak figures.
Figure 19: +12VA input from load tester at 750.4 W (69.6 mV).
Figure 20: +12VB input from load tester at 750.4 W (68.2 mV).
Figure 21: +5V rail with power supply delivering 750.4 W (27.6 mV).
Figure 22: +3.3 V rail with power supply delivering 750.4 W (18.4 mV).
Now let’s see if we could pull more than 750 W from this unit.