Seventeam ST-550P-AG Power Supply Review

Overload Tests

Before overloading power supplies we always test first if the over current protection (OCP) circuit is active and at what level it is configured.

In order to do that we first removed the auxiliary video card power cable from our load tester to make the +12V1 from the power supply to be connected on the +12V1 input from our load tester and the +12V2 from the power supply to be connected on the +12V2 input from our tester (with the video card cable connected the +12V1 input was connected to both +12V1 and +12V2 rails from the power supply).

Then we configured our load tester with a low (1 A) current on +12V1 and increased current at +12V2 until the power supply shut down. This happened when we tried to pull more than 28 A from +12V2.

Even though OCP was clearly active, we think that it was configured at a value that is too high, since the label states an 18 A limit for each rail. Maybe the value is too high on purpose, since the +12V2 rail is connected to the CPU (EPS12V/ATX12V connector) and to the video cards at the same time, what would shut down the power supply under normal working conditions. In our opinion Seventeam should have moved the video card or the CPU connector to +12V1 and configured OCP at a lower value.

Then starting from test six we increased currents on +12 V, +5 V and +3.3 V to the maximum we could with th
e power supply still running inside ATX specs. The results are below. When we tried to increase one more amp at any output ripple would go to the roof, meaning that the unit stopped working correctly.