Seasonic FOCUS Plus 850 Gold 850W (Page 3 of 4) | Reports

Page 3 - Physical Look - Inside

As we usually do, we opened up the Seasonic FOCUS Plus 850 Gold 850W power supply to take a closer look at what is going on inside. Opening up this power supply will void your ten year warranty, as the warranty seal covers one of the screws. For your benefit, we voided our warranty on this unit, so you do not need to. There are zero user serviceable parts inside anyway. Removing the top shell from the FOCUS Plus 850 Gold 850W is pretty easy, as we just remove the four screws at the top. The OEM for the Seasonic FOCUS Plus 850 Gold 850W is obviously Seasonic. However, this is a different platform from the most recent Seasonic power supply we reviewed, the Seasonic PRIME Titanium 850W. The photo above shows an overhead view of its internal components. Build quality is pretty good, even with a few patches of glue globs. Seasonic has always had an excellent reputation for power supplies, so we will see how this affects the build quality. Otherwise, there are many heatsinks found here left in a natural silver finish.

The transient filter stage is the first input stage of any computer power supply, so we will take a closer look at this first. From here, there are two ferrite coils and one metal oxide varistor. One X-capacitor can be found here at the AC receptacle in addition to two Y-capacitors. Another set of one X and two Y-capacitors can be found near the area, making for more than twice the amount of X and Y capacitors than recommended. In addition, the MOV being present here is good, as they are intended to protect your power supply from AC line voltage spikes.

On the primary side there is one Nippon Chemi-Con capacitor. It is rated at 650uF at 400V. It has a temperature rating of 105c. It is great to see Japanese brand capacitors here, as some cheaper units have capacitors made from Taiwan or China. I am also happy to report the higher 105c temperature rating, as they generally boast a longer lifetime.

The power supply uses one GBU15L06 rectifying bridge attached to a heatsink, supporting up to 15A of current at 115c. At 115V, the theoretical power you can pull from the bridge rectifier is 1725W at 100% efficiency. Of course, this is purely from the bridge rectifier, and not all components in the power supply can actually hold this workload. Even so, this is well above the necessary requirements for an 850W power supply. The active PFC circuit in the Seasonic FOCUS Plus 850 Gold 850W is controlled by a Champion CM6500 PFC chip. Other components in the active PFC circuitry were pretty easy to get a closer look at. First are two Infineon IPP50R190CE power transistors. These transistors are rated to deliver 15.7A at 100 degrees Celsius continuously. A single STMicroelectronics STTH8S06D diode is also found in the active PFC circuit. Four Greatpower GPT13N50DGN220FP MOSFET transistors are the main switchers, with the Champion CM6901 as the PWM controller. Each GPT13N50DGN220FP can deliver up to 13A at 100 degrees Celsius continuously, with a maximum resistance of 0.49 ohms. This on characteristic is called Static Drain-Source On-Resistance or commonly abbreviated as RDS(on). The more efficient the component is, the lower the RDS(on) value, since it wastes less power with lower resistance.

As for the secondary side, there are quite a few more Japanese capacitors made all from Nippon Chemi-Con, including both the electrolytic and polymer capacitors. The electrolytic capacitors are all rated at least 105c. As with modern high efficiency power supplies, all rectifiers produce the +12V out -- while the +5V and +3.3V outputs are generated from the +12V output using a DC to DC converter within the power supply unit. The +12V output is regulated by four Nexperia, formerly known as NXP Semiconductors, PSMN2R6-40, cooled by the chassis. Drain source voltage is rated at 40V, with a continuous drain current of 100A at 25c. An RDS(on) value of 0.0028 ohm maximum and 0.002 ohm typical are provided. The +5V and +3.3V rails are powered by components on a daughterboard, which unfortunately cannot be viewed due to a metal heatsink being directly attached here. Finally, a Weltrend WT7527V IC provides over/under current and over/under voltage protection. The datasheets for all components mentioned in this review can be found on their respective manufacturer's websites.

At the back, we have a large daughterboard covering the entire rear panel. This is where the modular cable sockets go. Layout of the output connectors can be found on the previous page. Seasonic has done a good job in ensuring quality is not sacrificed here. Soldering is excellent overall, which is nothing less than expected for this OEM. Component selection too is great with a decent layout for cooling. In addition, with the number of heatsinks in this unit, I doubt cooling will be an issue.

Speaking of cooling, the last component to look at is an important one, as it draws in air to let all these small components breathe easy. This is the Hong Hua fan connected to the mainboard of the power supply. It should be noted this is a semi-passive power supply, as the fan only kicks in at higher loads. Further research of the HA1225H12F-Z shows this fan operates at 12V and 0.58A, with a speed of 2200RPM, and with fluid dynamic bearings for quieter operation.

Page Index
1. Introduction, Packaging, Specifications
2. Physical Look - Outside
3. Physical Look - Inside
4. Minor Tests and Conclusion