Load Testing: Regulation
A decent load test of a PSU requires a decent load. Contrary to what some may believe, that means you need a known load that can fully stress the PSU. Computer hardware does not cut it. Worse, if the PSU fails during testing it might take out the computer hardware anyway. Commercial load testers cost a lot of money. I do not have a lot of money, so I built my own with juicy power resistors and a Toyota cylinder head. It works great. I’ll be using it to load this thing down fairly severely and will check voltages
and ripple (more on that later) at various points. The down side to my tester is that the loads it can put on PSUs are fairly coarse, they go in increments of 48 W for 12 V, 50 W for 5 V and 22 W for 3.3V. Those wattages assume the PSU is putting out exactly the official rail voltage, a PSU putting out 12.24 V rather than 12 V will be at 49.9 W per step rather than 48 W. I file that under the “tough beans” category as I figure if a percent or two of load makes that much of a difference, the PSU manufacturer should have hit the voltage regulation more squarely. It does make calculating efficiency difficult at best. However, given that the input power is read via a Kill-a-Watt, the efficiency numbers are dubious to begin with. Kill-a-Watts are not known for extreme accuracy on things with automatic power factor correction. For this reason, I am not listing the efficiency.
The ATX spec says that voltage regulation must be within 5% of the rail’s official designation, regardless of load. It doesn’t actually mention that the PSU shouldn’t explode, though I expect they figured it was implied. Exploding is a failure in my book regardless.
It is also worth knowing that I will be testing this PSU at both outdoor ambient temperatures (typically between 10 °C and 20 °C here this time of year) as well as in the Enclosure of Unreasonable Warmth. TEUW is a precision engineered enclosure that I use to route the exhaust air from the PSU right back into the intake fan, it is adjustable to hold the intake air temperature at (almost) any level I want it. This way I can test the PSU’s response to hot conditions as well as cold conditions. For the hot testing I will be running the intake temp as close to the unit’s maximum rated temperature as possible. TEUW, in case you’re curious, is a cardboard box.
| Wattages (total) | 12 V Rail | 5 V Rail | 3.3 V Rail | Kill-A-Watts | Temps In/Out |
| 0/0/0w (0w) | 12.11 | 5.03 | 3.36 | 8.8 | 14/16°C |
| 96/50/22w (168w) | 12.11 | 5.05 | 3.36 | 189 | 14/16°C |
| 288/50/22w (360w) | 12.11 | 5.06 | 3.37 | 392 | 14/18°C |
| 528/50/22w (600w) | 12.11 | 5.07 | 3.39 | 651 | 14/20°C |
| 768/50/22w (840w) | 12.10 | 5.08 | 3.39 | 917 | 14/25°C |
| High Temperature Results Below: | |||||
| 768/50/22w (840w) | 12.09 | 5.08 | 3.40 | 924 | 41/43°C |
Here we go, the meat of the thing. The 12V rail came in at 0.16% regulation, which is fantastic. The 5V rail came in at 1% (0.994 if you’re feeling accurate), while the 3.3V rail “only” managed 1.2%. Combined that gives us 0.8% regulation, which is fantastic.
The fan was very quiet up till sustained full load, at which point it was still quite quiet. In the heat the fan ramps up significantly, at full load it’s not exactly quiet, but not bad by any means.
If the Kill-A-Watt is reading correctly (I have my doubts on this one) efficiency is close to or over 92% from test three onwards. That would be awfully impressive for a unit rated as Gold, I suspect that the Kill-A-Watt was confused by the APFC.
In any event, this is an easy, and excellent, pass.
I tested SCP as well, and the PSU shut down quickly. Better than usual for a >750w single 12v rail PSU. Nice!
