Page 3 - Physical Look - Inside
To begin our internal inspection of the Thermaltake Smart BM3 850W, I opened up the PSU. Please note doing this at home may void your 5-year warranty thanks to a seal that extends over one edge of the power supply. But for your benefit, I disassembled mine, so you do not need to. There are no user-serviceable parts inside.
Taking apart the Thermaltake Smart BM3 850W was not the most straightforward, with two screws at the top next to the fan mount and four screws around the side underneath the labels. The photo above shows an overhead view of its internal components. It features an LLC full bridge topology with DC-to-DC converters. At first glance, the build quality appears to be passable. There are two main heatsinks inside, with both being unpainted aluminum.
Starting with the transient filter stage, we find ourselves with two metalized polyester X-capacitors, two ceramic Y-capacitors, two ferrite coils, and one metal oxide varistor or MOV. This is two times the number of X-capacitors than recommended, which is always nice to see. It is also great to see the MOV, which is used to protect the power supply from AC voltage spikes. Not all modern power supply units have one, so it is good to spot one here.
On the primary side, we can see a single Japanese brand Nichicon capacitor. The Thermaltake Smart BM3 850W power supply incorporates one 820uF x 400V capacitor. This Nichicon capacitor is rated at 105 degrees Celsius, which is better than the more value-oriented 85 degrees Celsius rated capacitors in many budget power supplies.
The active power factor correction or APFC circuit uses a single GBU2506L rectifier bridge attached to the first heatsink. We were not able to identify the brand of the rectifier bridge. Judging by standard rectifier bridge naming conventions, at 115V, it has a rated current of 25A, so you can theoretically pull 2875W (25A * 115V * 1 diode). This, of course, is limited to the fact that it is not 100% efficient, just like any electrical component or device. This also neglects the fact that other components are unable to keep up. Either way, this far exceeds the 850W this power supply unit is rated for.
Further up, there are two power transistors directly attached to the largest heatsink along with an APFC boost diode. On the opposite side of the Nichicon capacitor are the main switchers. However, due to the tight spacing of components, I was unable to make out any codes on the power transistors other than the fact they are made by Lonten, a Chinese brand. As per usual though, it is important to note that the lower the resistance on the transistors is, the more efficient the components will be. This is because the Static Drain-Source On-Resistance, or RDS(on), will dissipate power as heat, so the smaller the resistance, the less power wasted. Another important component to note is the Champion CM6800UX PFC controller located at the bottom of the main printed circuit board.
On the secondary side, we have a collection of smaller capacitors all rated at 105 degrees Celsius. There is a mix of Chemi-Con and Rubycon capacitors here, which are both Japanese brands. This is a pleasant surprise, since they only claim to have a Japanese brand primary capacitor. Having them on the secondary side adds to the quality of the Smart BM3 850W, although this is not guaranteed to be the case for every unit.
We have four CRMicro CRTD055N03L switching MOSFETs responsible for generating the +12V outputs at the back. Upon pulling up the datasheet, this reveals the continuous drain current for these devices is 61A at 100 degrees Celsius. The typical RDS(on) value is 4.3mΩ and the maximum RDS(on) value is 5.5mΩ. For the +5V and +3.3V outputs, once again due to how tightly the components are placed, I was unable to see their part numbers. While not seen outwardly, we have two ANPEC APW7164 synchronous buck controllers. The datasheet for all the components mentioned is found on their respective manufacturer’s websites.
At the end of the circuit, we have the area where all the fixed cables are connected and lead outside of the Thermaltake Smart BM3 850W. Modular sockets are placed on a daughterboard at the back. This is standard for a semi-modular power supply with nothing of note.
Overall, the internal build quality of the Thermaltake Smart BM3 850W is likely passable given what was promised. The use of Japanese brand capacitors was nice, as they are always reliable. The other components found are mostly Chinese brand parts when we were able to dig up the information. The amount of glue globs was excessive in my opinion, and all the components were more squished together. With what could be seen of the circuit board was clear and readable though.
In terms of cooling, there are two things we need to pay attention to for a power supply unit, namely the heatsinks and cooling fan. In this case, we can see two large heatsinks and one cooling fan inside the Thermaltake Smart BM3 850W. When it comes to cooling, the Thermaltake Smart BM3 850W uses a Thermaltake TT-1225 fluid dynamic bearing fan. The size of the fan is 120mm in diameter, which is the maximum size the enclosure can accommodate. It is rated for 0.35A at 12V.
Page Index
1. Introduction, Packaging, Specifications
2. Physical Look - Outside
3. Physical Look - Inside
4. Minor Tests and Conclusion
