Seventeam ST-420BKV 420 W Power Supply Review

Overload Tests

After these tests we tried to pull even more power from Seventeam ST-420BKV. 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 44° C and the power supply was working at 50° C.

We tried to pull even more power, but the power supply shut down, showing the over power protection (OPP) in action. We could also see the over current protection (OCP) in action in two ways. First we tried to determine if the OCP circuit was active and at which level. For this we configured our load tester to pull a lower current from +12V1 (5 A) and we increased the current on +12V2 until the power supply shut down. We found out that if we pulled more than 18 A from +12V2 the power supply would shut down, so OCP was set at 18 A, 2 amps above what was written on the power supply label, which is normal. Then we tried to pull 18 A from the two +12 V rails at the same time, but the power supply would shut down. Then we remembered that the manufacturer says on the label that the maximum combined current on +12 V is 24 A. The maximum we could pull was 15 A on each rail (30 A total), so the OCP circuit was again configured a little bit above from what was written on the label.

The bottom line is: both OPP and OCP circuits are active and working just fine. As we mentioned, when we tried to pull more power the unit would shut down or simply not turn on. ST-420BKV survived our tests.

Short-circuit protection is also working just fine, as we could test.

We could set the power supply to deliver more power, but it would shut itself down after a couple of minutes.

Under this condition noise level continued within specs, at 29.4 mV on +12V1, 25.6 mV on +12V2, 24.8 mV on +5 V and 19.6 mV on +3.3 V. This is really good.

The main problem of running this power supply at 450 W is its efficiency, below the 70% mark. As you can see, we were pulling 660 W from the wall to produce 450 W.

Figure 18: Noise level at +12V1 with power supply delivering 450 W.

Figure 19: Noise level at +12V2 with power supply delivering 450 W.

Figure 21: Noise level at +5 V with power supply delivering 450 W.

Figure 22: Noise level at +3.3 V with power supply delivering 450 W.

Another great feature about this power supply is its fan. When the power supply is cool, it runs very slowly, making almost no noise. But as soon as the power supply temperature reached 30° C the fan started spinning faster, making a lot of noise.