Foxconn WinFast FA-550A (550W)
We already tested the WinFast FA-550A power supply on our site and you can refer to our article called Power Supply Units from Foxconn and Hiper Group in Our Lab for details about its interior and exterior design.
The last time, however, the FA-550A had a very poor result in our cross-load characteristic test despite its independent voltage regulation. The +3.3V voltage quickly left the allowable range preventing the PSU from yielding the declared output power even.
That was rather strange for a PSU of that class, especially since other PSUs from Channel Well Technology (this company sells its produce under the Foxconn brand) did much better. I mean the FA-380A unit mentioned in the previous review and the Antec TruePower True430P model which is also manufactured by CWT.
That’s why I suspected I dealt with a defective sample of the PSU, and CWT has been kind to offer us another sample of the FA-550A model. This sample is absolutely the same as the earlier tested one in its specification and internal design, so I won’t describe it once again. I’ll just give you the cross-load diagram for this sample:
As you see, it is all much better now. The cross-load diagram fully covers the allowable range of output power for this PSU, just like it has to for a PSU with independent voltage regulation. Moreover, the diagram nearly coincides with the diagram for the above-mentioned Antec True430P: excellent stability of the +5V voltage (which almost remains constant) and good stability of the +3.3V and +12V voltages.
The voltage ripple at full load was near 20 milliseconds on the +5V rail (it was only high-frequency ripple without a 100Hz constituent), near 30 millivolts on the +3.3V rail (high- and low-frequency alike), and near 45 millivolts on the +12V rail (both low-frequency and high-frequency pulsations).
So, I can remove all the blame from the Foxconn WinFast FA-550A power supply, but of course I can’t say how frequently you can meet a sample with poor +3.3V stability. However, considering the results of the tests of a WinFast FA-380A and an Antec Tru430P, based on the same components, I’m inclined to think this is rather a rare problem.