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) | 12.34 | 5.09 | 3.37 | 7.2 | 13/17°C |
| 96/50/22w (168w) | 12.34 | 5.02 | 3.33 | 188 | 13/18°C |
| 240/50/22w (312w) | 12.33 | 5.02 | 3.33 | 347 | 13/20°C |
| 384/50/22w (456w) | 12.33 | 5.00 | 3.33 | 536 | 13/23°C |
| 528/50/22w (600w) | 12.30 | 5.01 | 3.33 | 679 | 13/26°C |
| High Temperature Results Below: | |||||
| 528/50/22w (600w) | 12.26 | 5.00 | 3.32 | 681 | 43/57°C |
This looks pretty nice, we get 0.65% regulation on the 12V rail, excellent! The 5V rail comes in at a respectable 1.8%, while 3.3V manages 1.5%. All averaged together we get 1.3% regulation, that’s a bit short of the 1% “excellent” line, but not by a lot. It’s certainly quite good and nothing to argue about at all!
The temperatures point towards the efficiency of the unit, at no time during the first test run could I hear the fan at all, not even with my head inches away from it. Once I ramped the intake temperature up to 43°C (as high as I could get it) the fan sped up a bit and was audible, but extremely quiet. We’re talking really really really quiet here, very impressive indeed. People who are after silence take note, this thing is QUIET!
