Overload Tests

After these tests we tried to pull even more power from Corsair TX750W. Below you can see the maximum amount of power we could extract from this unit keeping it working with its voltages and electrical noise level within the proper working range. During this test room temperature was of 45° C and the power supply was working at 45° C.

Input Maximum
+12V1 33 A (396 W)
+12V2 33 A (396 W)
+5V 10 A (50 W)
+3.3 V 10 A (33 W)
+5VSB 3 A (15 W)
-12 V 0.8 A (9.6 W)
Total 900 W
% Max Load 120%
AC Power 1,111 W
Efficiency 81%

Here noise level at +12 V output reached 112 mV, a value that is touching the 120 mV limit, showing us that this power supply obviously wasn’t designed to operate under such high specs.

Corsair TX750WFigure 22: Noise level at +12V1 input from the load tester at 900 W.

We were not only impressed by the fact that a power supply labeled as a 750 W product could deliver 900 W but also because it could maintain an efficiency over 80% under this circumstance. But, as we mentioned, we were not happy with the electric noise level.

Another thing worth mentioning is the thermal dissipation of this power supply. Even under this extreme condition the power supply temperature was only two degree Celsius higher than the room temperature inside our “hot box,” showing that the 140 mm fan used by this product works very well. During our tests we could see its speed changing as the power supply temperature increased. Another very important feature present on this power supply is the fact that its fan will continue spinning even after the computer is turned off – assuming that you don’t turn off the power supply master switch –, which is really great, as it will keep cooling down the power supply until it reaches a “safe” temperature. The fan will spin at a lower speed, so you can’t even hear it spinning when this happens. In theory this feature increases the life span of the product.

Short-circuit protection for both +5 V and +12 V outputs worked just fine, but it seems, however, that this power supply doesn’t have over current protection (OCP), or it is set way over 66 A (the maximum amount of current we pulled from the +12 V output) – while according to the power supply label the limit for the single +12 V rail is of 60 A.

As for the over power protection (OPP), we pulled way over the maximum power supply labeled power and the power supply didn’t shut down. In fact, when we tried to pull even more power from this unit (i.e., when we tried to pull more than 10 A from +5 V and +3.3 V) the circuit breaker here at our lab disarmed. We wanted to see our power supply disarming, not the circuit breaker.

Gabriel Torres is a Brazilian best-selling ICT expert, with 24 books published. He started his online career in 1996, when he launched Clube do Hardware, which is one of the oldest and largest websites about technology in Brazil. He created Hardware Secrets in 1999 to expand his knowledge outside his home country.