Seasonic has just released a series of fanless power supplies with the 80 Plus Gold certification, full modular cabling system, and single +12 V rail. They released two models so far: 400 W and 460 W. Let’s take an in-depth look at their 400 W model.

The new X Fanless series shares the same design concepts from the “standard” Seasonic X series, like the use of a resonant switching circuit, the use of a synchronous design in the secondary with DC-DC converters for the +5 V and +3.3 V outputs, the installation of the DC-DC converters directly on the modular cabling system, and some connectors of the modular cabling system soldered directly on the main printed circuit board.

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Figure 1: Seasonic X-400 Fanless power supply

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Figure 2: Seasonic X-400 Fanless power supply

The Seasonic X-400 Fanless is 6.3” (160 mm) deep and, as the name implies, it doesn’t have any kind of fan, being a product target to users that want to build the quietest computer possible.

This unit features active PFC, of course.

The new Seasonic X-400 Fanless has a full modular cabling system, meaning that even the main motherboard cable is modular. This system has seven connectors and the power supply comes with the following cables:

• Main motherboard cable with a 20/24-pin connector, 23.6” (60 cm) long
• One cable with two ATX12V connectors that together form an EPS12V connector, 25.6” (65 cm) long
• One cable with one six/eight-pin connector for video cards, 23.6” (60 cm) long
• One cable with three SATA power connectors, 21.3” (54 cm) to the first connector, 5.9” (15 cm) between connectors
• One cable with two SATA power connectors, 21.3” (54 cm) to the first connector, 5.9” (15 cm) between connectors
• One cable with three standard peripheral power connectors, 21.3” (54 cm) to the first connector, 5.9” (15 cm) between connectors
• One cable with two standard peripheral power connectors, 21.3” (54 cm) to the first connector, 5.9” (15 cm) between connectors
• One adapter to convert one standard peripheral power connector into two floppy disk drive power connectors

All wires are 18 AWG, except the ones used on the ATX12V/EPS12V  and on the video card auxiliary power cables, which are thicker (16 AWG).

The cable configuration is satisfactory for a 400 W product, and the cables are very long for a 400 W unit.

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Figure 3: Cables

Let’s now take an in-depth look inside this power supply.