Before performing our overload tests we always like to test first if the over current protection (OCP) circuit is really active and at what level it is configured.

We configured +12V1 input from our load tester with a low current (1 A) and increased current on +12V2 input (which was connected to the power supply +12V1 rail thru the EPS12V connector) until the power supply shut down. This happened when we tried to pull more than 32 A, so OCP was active and set at 32 A. A value that is too high in our opinion, as the power supply label says that each rail has a limit of 18 A. We prefer when the over current protection is configured to a value closer to what is printed on the product label.

Unfortunately this power supply does not feature over power protection (OPP).

Then we tried to pull even more power from TruePower Quattro 850 W. The problem, however, was the noise level. As you know we were already facing noise issues with the power supply delivering 850 W. We could pull even more power from this unit, but noise level was always outside the maximum admissible according to the ATX standard (maximum of 120 mV for +12 V outputs and 50 mV for +5 V and +3.3 V outputs). The main problem was with the +5 V and +5VSB outputs. While noise level at +12 V outputs was high, it was still below 120 mV. Noise at +5 V, however, was at least at 70 mV and at +5VSB was at 87 mV.

So we can’t consider that we could successfully pull more power from this unit, as we can only consider results where the power supply is still working within ATX specs.

Short circuit protection (SCP) worked fine for both +5 V and +12 V lines.