Page 3 - Physical Look - Inside
We opened up the Cooler Master GX III Gold 850W to take a closer peek inside. Doing this at home may void your 10-year warranty, since it will break the warranty sticker on the side of the power supply. The 10-year warranty is the industry standard at this point, and it is excellent to see it continued on the Cooler Master GX III. To open the power supply to the above extent, eight screws need to be removed. The first four screws remove the initial cover for the power supply, and the next four remove the bracket holding the fan in place, which then reveals the internals. There are a few more steps to remove the entirety of the power supply from the enclosure.
The OEM for the Cooler Master GX III Gold 850W is Lite-On, which manufactures all sorts of power supplies for smaller and larger systems, but not too common in the ATX form factor. Their products range from gaming consoles, computers, industrial computers, and communication equipment. The power supply features a half bridge LLC topology with DC-to-DC converters. Cooler Master also included some styling with the internals, including two purple heatsinks. These are anodic-coated, and according to Cooler Master, this provides up to a 5-degree Celsius reduction in temperature.
Starting with the transient filtering stage, where the PSU is plugged in from the wall, there are two X capacitors and two Y capacitors. There are also two CM chokes in the power supply, with one metal-oxide varistor located in this area as well. The Cooler Master GX III Gold 850W is equipped well in this first filter stage. The MOV will ensure spikes from the AC line are balanced out, providing the needed stabilization.
The bridge rectifiers found on the Cooler Master GX III Gold 850W are the Diodes Incorporated GBU25KH. There are two of these found on opposite sides of the smaller purple heatsink in the above picture. The average forward rectified current capacity for the GBU25KH is 25A, which at 115V will provide up to 5750W (25A * 2 diodes * 115V), but is not reflective of the real-world conditions of the limitations of other components, and the bridge rectifier themselves not having 100% efficiency.
Along the larger heatsink, we can spot a WeEn Semiconductors NXPSC06650X silicon carbide boost diode. Two Infineon IPA60R099P7 power MOSFETs with rated drain current specifications of 20A at 100c can be seen here as well. The maximum resistance for these is 99mΩ, while its typical resistance is 77mΩ. This on characteristic is called Static Drain-Source On-Resistance, or commonly abbreviated as RDS(on). These lower resistance numbers mean power the supply is more efficient, since less resistance means less power is wasted.
Continued at the primary side, we find a Japanese brand Toshin Kogyo capacitor. Cooler Master claims to have Japanese brand capacitors, so we should not be surprised by this find. The capacitor is rated for 680µF at 450V, rated for 105c. The higher temperature rating is at least one indication of a higher quality capacitor, since more budget friendly PSUs will go for 85c rated models.
The main switchers for the Cooler Master GX III Gold 850W are two Infineon IPA60R120P7, each rated for 16A at 100c. These MOSFETs have a maximum resistance of 120 mΩ and typical resistance of 100 mΩ.
On the secondary side, we find twelve Jamicon TK-series capacitors rated 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 +5.5V and +3.3V MOSFETs are located on the vertical board, and there are two sets for each. The first two are the Fairchild FDD8896, rated at 94A at 175c. It has an RDS(on) value of 5.7 mΩ maximum and 4.7 mΩ typical. Meanwhile, the other two are Fairchild FDD8880, rated at 58A at 175c, with an RDS(on) value of 9 mΩ maximum and 7 mΩ typical. Below these four Fairchild components, we find the PWM controller, an Anpec APW7159C. A Weltrend WT7527RA supervisor IC can be spotted on this board as well.
There are six +12V MOSFETs located underneath the mainboard. These are the Nexperia PSMN2R2-40YSD MOSFETs, rated at 180A at 25c, 10V. Their RDS(on) value is 2.2 mΩ maximum and 1.9 mΩ typical.
After inspecting the inside of the Cooler Master GX III Gold 850W power supply, the build quality appears to be excellent. Wires running around inside is minimized to provide the best cooling possible. Furthermore, soldering is done well to keep everything clean and neat. The component selection is acceptable for the performance class it is in.
The fan found in the case is a Yate Loon D14SH-12 fluid dynamic bearing fan. The D14SH-12 is 135mm in diameter and connected via a 2-pin connector to a daughterboard. A higher quality fan is preferred in my opinion. The fan can spin up to 1900 RPM, providing the necessary airflow to cool down the power supply under load. As mentioned previously, the fan will only kick in automatically once the load reaches at least 40%.
Page Index
1. Introduction, Packaging, Specifications
2. Physical Look - Outside
3. Physical Look - Inside
4. Minor Tests and Conclusion
