Even though power supplies from Seventeam aren’t sold in the USA retail market, they are very popular in several other countries, due to its low cost. In fact, it seems that Seventeam is the OEM manufacturer for some other brands – we discovered that the external power supply series from XG/MGE, Magnum, is in fact Seventeam Fanless series. ST-420BKV is a 420 W power supply without PFC. Let’s take an in-depth look at this power supply to check whether this unit is good or not and test it to see if it can really deliver its announced 420 W.

Even though its design resembles a high-end product – using a big 120 mm fan on its bottom and using a mesh on the back –, ST-420BKV finishing isn’t so good. Even though on Seveteam’s website this power supply is pictured as having a black automotive painting job and an orange fan, the model we bought for this review used a plain zinc-coated steel housing, making it to look like a very low-end unit.

Seventeam ST-420BKVFigure 1: Seventeam ST-420BKV.

On the other hand this power supply has a feature we’ve never seen before: a 12 V jack for powering external devices such as speakers and external hard disk drives (see Figure 2).

Seventeam ST-420BKVFigure 2: Seventeam ST-420BKV.

In Figure 2 you can also see that this power supply has a 110/220 V switch, indicating that it doesn’t have PFC circuit (power supplies with active PFC don’t have a 110/220 V switch).

Even though this is a low-end power supply, the main motherboard cable (and only this cable) uses a plastic sleeving.

In Figure 3, you can see a big finishing detail missing: the cables come out from a big hole on the power supply housing and there is no finishing to cover the unused space, so you can see a big hole there.

Seventeam ST-420BKVFigure 3: Big uncovered hole.

This power supply has four peripheral power cables: one Serial ATA power cable containing two SATA power connectors; two peripheral power cables containing two standard peripheral power connectors and one floppy disk drive power connector each; and one peripheral power cable containing two standard peripheral power connectors. This power supply doesn’t have any auxiliary PCI Express power connector, so you will need to use an adapter in order to power your high-end PCI Express video card.

The main motherboard cable has a 20-pin connector, with a 4-pin extension in order to transform it into a 24-pin connector.

Seventeam ST-420BKVFigure 4: Main motherboard power connector.

The gauge of the wires used on all cables is 18 AWG, but the floppy disk drive connectors use 22 AWG wires.

Even though this power supply has an UL label, the model we’ve got didn’t have any UL registration number. However, Seventeam contacted us and sent us the complete UL documents, explaining that this model is really UL-certified and their registration number is E141400. We could confirm that online.

We decided to fully disassemble this power supply to take a look inside.


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.