Corsair HX750w (750w) ATX PSU
Simulated Load Testing
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To provide accurate and consistent results in all of our PSU testing, Overclock3D uses professional grade DCÂ electronic load equipment capable of placing a sustained load of 3690w across a total of six rails (including +5vsb and -12v) on the PSU! This is achieved by using a combination of SunMoon and Analogic electronic load equipment which allow us to adjust amperage loads in increments as small as 0.01A while also measuring voltage and wattage readings on-screen.
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During today’s tests, we will be placing the Corsair HX750W under 25%, 50%, 75% and 100% load levels at both room temperature and inside a hot box regulated to a temperature of around 50°C. Additional ‘Cross Load’ and a ‘Max Load’ tests will also be performed under these conditions to simulate how the PSU reacts to heavily uneven loads as well as running above its specified output.
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Corsair HX750W Results @ Room Temperature
 DC Watts
 Exhaust
(Low)
188w
39.3°C
(Med)
376w
45.0°C
5.07v
(High)
563w
48.5°C
(Full)
748w
51.8°C
(x-load)
159w
35.9°C
(x-load)
750w
50.4°C
(MAX)
913w
54.5°C
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Comparing the results in tests 1-4 with those of the HX850w, there really is very little difference between the two units. The voltages show roughly the same amount of droop from 25% (Low) to 100% (Full) load and efficiency is highest in tests 2 and 3 at around 93%, while tests 1 and 4 also do extremely well at around 91% efficiency. Intake and exhaust temperatures are the only areas which show significant difference to that of the HX850w, but this is more than likely down to our recent upgrade to a Fluke 52-II digital thermometer which is hooked up to two ‘K’ type thermal probes for more accurate delta temperature readings.
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Cross-load tests 5 & 6 tell a very similar story to that of the HX850w, with the voltages and efficiency levels once again being pretty much a mirror image. The lowest efficiency level is seen in test 5 with the unit dropping down to 84.12%, but the scenario of a PC system using over 170w on the +3.3v and +5v rails and only 12w on the +12v rail isn’t something that you’re ever likely to come across in the real world.
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Finally in test 7 the HX750w was pushed as far as it could go without OCP (Over Current Protection) kicking in and switching the unit off. This is the one test that could actually tell us if the HX750w is simply a re-badged HX850w, or if indeed there are some minor differences inside the unit that give it its 100w lower power output. With a whopping 21A load on both the +3.3v and +5v rails and 59AÂ on the +12v rail, the HX750w topped out at a total of 913w. This is of course WELLÂ above its rated output, but still a little below that of the HX850w which managed an amazing 1084w before showing signs of weakness. However, even at these extremely high loads, the HX750w managed 90.12% efficiency along with some rock solid voltage outputs.
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Corsair HX750W Results @ 50c
 DC Watts
 Exhaust
(Low)
188w
55.3°C
(Med)
376w
58.7°C
5.07v
(High)
563w
61.6°C
(Full)
747w
64.8°C
(x-load)
159w
55.0°C
(x-load)
749w
60.8°C
(MAX)
887w
66.0°C
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Bumping up the ambient temperature to a toasty 50°C and re-running the room temperature results, hardy anything at all changed. In fact, aside from the odd +/-0.2v fluctuation on a couple of the rails and a few dips in efficiency, the only real thing worth talking about is the MAX load test which topped out at 887w – 26w lower than in the room temperature tests. This is by no means anything to get upset about as the HX750w is still operating at 137w above its rated capacity, and with 88% efficiency too.
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Corsair HX750W Scope Results @ 50c
(Low)
(Med)
(High)
(Full)
(x-load)
(x-load)
(MAX)
Finishing up the testing, snapshots of the HX750w’s +3.3, +5 and +12v rails were taken using a Rigol 25Mhz 400MSa/s oscilloscope while installed inside the 50°C hot box. Unfortunately there’s not enough room on the page to put these side-by-side with the results from the HX850w, but if you’re interested, the 850’s results can be found here.
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Once again the HX750w closely resembles that of the HX850w giving stunning results with the +3.3v and +5v rails staying at or below 10mV ripple in tests 1-6 and only hitting 12mV ripple in test 7 on the +5v rail. The +12v rail was also extremely clean with ripple starting at 12mV in test 1 and only increasing to 40mV by test 4. Test 7 saw the ripple hit 52mV, which is 10mV higher than that of the HX850w, but still way below the maximum of 120mV as specified by ATXÂ standards.
