Seasonic SS-400HT power supply, 80 Plus version

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The Seasonic SS-400HT Active PFC F3 has a utilitarian appearance. The casing is the traditional gray, as befits an OEM product.

A flush wire grill is fitted over the 120mm fan.

The hexagonal hole pattern found on other Seasonic 120mm fan PSU exhaust grills is used here. There are some vents other than the exhaust grill, including the four small slots in the photo above, and the row of slots on the inside panel shown below.

One can only assume these exhaust slots are near hot components to ensure there is some airflow across them. Because of the right angle juxtaposition of the fan and the main exhaust vent, there is considerable back pressure and turbulence that might cause this back corner edge to get poor airflow. These slot help overcome any potential cooling issues.

The interior is identical to the Seasonic S12-500 and 600, as far as we can see. The fins from each heatsink are staggered in two double rows for what is arguably the highest cooling surface area of any fan-cooled power supply we've tested.

Inventive heatsink fins for arguably the highest cooling surface area of any fan-cooled power supply.

Familiar tidy inductors and layout.

Same fan as in the S12-500 / 600.

The fan is the same one used in the S12-500 / 600, which means it's slightly noisier than the one used in the S12-330, 380 and 430. We cannot expect this model to break new quiet records, but it should be at least as quiet as the S12-500 / 600.


There are a total of six cable sets plus a fan RPM cable to provide fan speed information to the motherboard:

  • 11" cable for main 24-pin ATX connector
  • 12" cable w/AUX12V connector
  • 12" cable w/8-pin EPS12V connector
  • 2 x 26" cable with three 4-pin IDE drive connectors and one floppy drive power connector
  • 22" cable with two SATA drive connectors
  • 24" cable fan monitor with 3-pin connector for motherboard fan header

The main cables are short, which is typical for OEM PSUs.

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