Seasonic SS-300TFX is a small 300 W power supply following the TFX12V form factor, targeted to small form factor (SFF) computers, carrying the 80 Plus Bronze certification. Let’s see if it is a good buy.

One of the highlights of this power supply is obviously its reduced footprint, measuring only 6 7/8” x 3 3/8” x 2 ¾” (17.5 x 8.5 x 7 cm). It is cooled down by a slim 80 mm fan located on its top part and it feature active PFC circuit and thus has automatic voltage selection.

Seasonic SS-300TFX power supplyFigure 1: Seasonic SS-300TFX power supply.

Seasonic SS-300TFX power supplyFigure 2: Seasonic SS-300TFX power supply.

The reviewed power supply doesn’t have a modular cabling system and it comes with the following cables:

  • Main motherboard cable with a 20/24-pin connector, 13 3/8” (34 cm) long.
  • One cable with one ATX12V connector, 17 ¾” (45 cm) long.
  • Two cables with two SATA power connectors each, 9 7/8” (25 cm) to the first connector, 5 ½” (140 mm) between connectors.
  • One cable with two standard peripheral power connectors and one floppy disk drive power connector, 11 7/8” (30 cm) to the first connector, 5 7/8” (15 cm) between connectors.

As you can see, the number of connectors is very reduced and this unit doesn’t come with an auxiliary power cable for video cards. All wires are 18 AWG, which is the correct gauge to be used. It was really nice to see 18 AWG wires on this power supply, because usually manufacturers prefer to save and use thinner wires on low-wattage models.

Seasonic SS-300TFX power supplyFigure 3: Cables.

Now let’s take an in-depth look inside this power supply.

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.