A Look Inside & Component Analysis

Before reading this page, we strongly suggest a look at this article, which will help you understand the internal components of a PSU much better. Our main tool for the disassembly of the PSU is a Thermaltronics TMT-9000S soldering and rework station. It is of extreme quality and is equipped with a matching de-soldering gun. With such equipment in hand, breaking apart every PSU is like a walk in the park!





This unit uses Seasonic's new high-end platform with model number XP3. We already covered the platform in our recent review of the SS-1200XP3, which managed to impress us with its performance. This platform uses a full-bridge topology with an LLC resonant converter in its primary side, while DC-DC converters generate the minor rails and mosfets regulate the +12V rail in the secondary side. The main difference between the this unit and its larger sibling, the SS-1200XP3, is in Seasonic's use of FPCAP polymer caps on the modular board, over the Chemi-Cons in the SS-1200XP3. A shortage in their caps supply was apparently the reason behind the change, and it is of no consequence since, produced by Nichicon, all FPCAP products are also of high quality. Please note that the FPCAP brand initially belonged to Fujitsu, before they sold it to Nichicon.


A sealed PCB behind the AC receptacle holds a CM choke, four Y caps, and a single X cap. The EMI filter's other components, two pairs of X and Y caps, a CM and DM choke, and an MOV, are on the main PCB. There is also an NTC thermistor for protection against large inrush currents. Its electromagnetic relay helps it cool down quickly, while also increasing efficiency levels a bit since no energy is lost on the thermistor while the PSU operates.


Both parallel bridge rectifiers are bolted to a dedicated heatsink. Their model number is LVB2560 and both are manufactured by Vishay.


The APFC converter uses three Infineon IPP60R125CP fets and a single STPSC806D boost diode. The three parallel hold-up caps are provided by Nippon Chemi-Con (420 V; 330 μF each or 990 μF combined; 105°C; KMR series).


A small daughter-board holds the PFC controller, an NPC1654 IC.


The full-bridge topology uses four Infineon IPP50R250CP fets. An LLC resonant converter also boosts efficiency.


The LLC resonant controller, a Champion CM6901 IC, is hiding behind the bulk cap in the middle.


There is a quite large heatsink in the secondary side, but it doesn't have any mosfets attached to it. The latter are installed on the solder side of the main PCB, right below the aforementioned heatsink.


In total, four Fairchild FDMS015N04B fets are used, while the 1200 W model uses eight of exactly the same type, which is a huge difference for an additional 150 W.


The casing plays a significant role in cooling the +12V fets down.


All capacitors in the secondary side of the main PCB, polymer and electrolytic, are provided by Nippon Chemi-Con. We couldn't ask for anything better here.


Both VRMs designated to generating the minor rails are on the modular PCB, which reduced energy losses. Each of these holds three Infineon BSC0906NS fets, and an Anpec APW7159 PWM controller handles both regulators.


The front of the modular PCB only houses FPCAP polymer caps. The 1200 W model uses Chemi-Cons here. FPCAP caps are also Japanese and of very high quality, so we have absolutely no objection to Seasonic's cap choice.


The standby PWM controller is an ICE2QR4765 IC.


The supervisor IC, a Weltrend WT7257V, and the AS393 dual-voltage comparator are installed on this board. The WT7257V supports OCP for up to two +12V virtual rails, but this unit only has one.


Soldering quality on the main PCB is, as is typical of Seasonic, very good.


The cooling fan with model number 9S1212H403 is by Sanyo Denki. We couldn't dig up any detailed information on this particular fan so we had to ask Seasonic about it and the informed us that it uses a double ball-bearings and its lifetime may look low on papers but the 40,000 hours are for 100% load at 40°C ambient or for 80% load at 50°C. Most of you and us would prefer however an FDB fan with a larger diameter instead. Seasonic will hopefully rethink their fan choice in the near future. These Sanyo Denki fans may be quality products, but they are noisy because they have to rotate at higher speeds to efficiently remove the heat. A 140 mm fan would provide just as much airflow at lower speeds, which reduce noise output significantly.