Seasonic SS-350TGM Power Supply Review

Today we tackle something a bit off the beaten path for us; a low power non-ATX specification power supply from Seasonic. We do know that many of our readers build systems that are not like all the others especially when it comes to crafting smaller purpose driven boxes. The 300TGM may be just what you are looking for.

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Build Quality

The Seasonic SS-350TGM features a single 80mm fan design that is the preferred cooling solution by some brands. The major downside to this fan design is that to move a sufficient volume of air to cool a high output power supply, such as the OCZ ProXStream and PC Power & Cooling Turbo-Cool 1KW-SR, it must spin very fast resulting in elevated noise levels. While these 80mm designs are not great for quiet computing environments the key criteria in our evaluation is whether or not the cooling solution is sufficient, not necessary its sound level or form factor and our comments on such later are not absolute decibel values.

External Build Quality

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The exterior build quality of the Seasonic SS-350TGM is serviceable, but the looks are nothing to write home about compared to the retail products we usually review. As this is an OEM power supply, it is finished in a drab flat grey. The top of the unit features the 80mm fan at one extreme and a whole lot of gray on other. Other than that, the rear of the unit has the AC input receptacle but no on/off switch and the front of the unit has a pair of modular connectors where the one piece wiring harness connects. It’s flat, it’s dull, it’s boring, it’s OEM!

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The Seasonic SS-350TGM comes in at a total length of ~6 7/8 inches while the cables all reach out to ~13 to 16 inches to the first or only connector. None of the cables are sleeved. The full dimensions for those who are interested in the TFX form factor are 175mm (6.9") x 85mm (3.3") x 63.5mm (2.5"). As for applicability of this unit, many mini-ATX cases and some HTPC cases can use this form factor. So, while limited, there are options out there outside of the OEM applications (thin form factor HP/Dell/Etc.) for intrepid users.

Internal Build Quality

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Once we open the Seasonic SS-350TGM we are left looking at a very compact power supply compared to what we are used to seeing. Due to the form factor the arrangement of the unit is a bit different from normal with the primary is situated at the back of the unit and the secondary at the front. We can also see that the unit features a second horizontal PCB that sits above the main PCB. The design of the unit is another LLC resonant primary and a synchronous rectification with DC-DC VRM’s secondary. The single fan that cools the unit is an overhead fan like we have seen a number of times before, however it is a thin 80mm fan which is a first. This fan is provided by ADDA and rated at 0.26A at 12v. This is paired with five small aluminum heatsinks for cooling the unit.

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Starting on the primary side, we see that the input filtering begins on the PCB attached to the input receptacle with some X and Y capacitors along with a coil. It then continues on to the main PCB. Slightly behind the filtering components, we see a small heatsink which has the bridge rectifier attached to it. The heatsink just behind that on the edge of the PCB houses the PFC power components. Directly across the PCB from that is another heatsink which houses the main switchers. Between these two heatsinks sits the main input capacitor. This capacitor is provided by Rubycon and it is rated at 420v 220uF 105C. When we flip the main PCB over, we see that the soldering is very well done overall. We also see here that the 12v MOSFETs are on this side of the main PCB as we have seen from Seasonic with their X-Series units.

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Moving to the rest of the secondary, we see that there is a bit of a double stack here. The PCB on top houses the DC-DC VRM’s. These VRM’s are populated with solid capacitors from Nippon Chemi-con. Underneath this PCB are further parts of the secondary filtering made up of a number of Rubycon standard electrolytics and Nippon Chemi-con solid capacitors. Behind this area, near the main transformer, are a pair of heatsinks which are there for the 12v MOSFETs that are on the other side of the PCB that we already saw.

Build Quality Summary

The overall build quality of the Seasonic SS-350TGM is excellent for an OEM unit. For a retail unit, the exterior fit and finish leaves a few things to be desired. The flat grey finish is serviceable but let’s face it; it is ugly. The cables lengths are short for an ATX case, but appropriate for the smaller cases this unit will actually be used in. In all cases though, these are ugly being completely unsleeved. When we move to the interior of the unit, we see a very well constructed unit, especially considering the size restrictions. The topology is modern and in the same vein as the Seasonic X-Series units we have seen with an LLC resonant primary and synchronous rectification secondary with DC-DC VRMs. The integration is excellent and the component selection features standard Rubycon and solid Nippon Chemi-con capacitors. The one aspect of quality that we find is, perhaps, lacking is the inclusion of an ADDA fan in such an application that would benefit from a high quality fan. Let’s move on now to see how the unit does in our load testing.