A Look Inside

Before reading this page we strongly suggest to take a look at this article, which will help you understand the internal components of a PSU much better.


With the primary&secondary heatsinks removed the view is much clearer, don't you think? The OEM of the unit is HEC-COMPUCASE.


The first part of the transient filtering stage as usual starts at the AC receptacle. One X and two Y caps are located there. It continues on the main PCB with two coils, two Y&X caps and an MOV. The bridge rectifier, a KBU 10J, is bolted to a heatsink.


In the APFC stage two mosfets, FDP18N50, and the necessary boost diode are used. The smoothing/reservoir capacitor is provided by CapXon (330μF, 400V, 85°C). As primary switches we find two Infineon 20N60C3 mosfets. The combo PFC/PWM controller resides on a vertical daughter-board and once more is a Champion CM6800.


In the secondary, passive design is used for the regulation of all rails. The +12V rail is handled by two SBR30A50CT while 5V and 3.3V are generated by two STPS30L45CT. The presence of only two toroidal chokes indicates that group regulation is used so the bigger coil is shared by 12V/5V and the smaller one is for the rectification and filtering of 3.3V. All capacitors in the secondary are provided by Teapo and are labeled at 105°C. In the secondary side there is also the protections IC, a Weltrend WT7525, which is soldered on a daughter-board. It supports up to two +12V rails matching this way the number of PSU's +12V rails. The odd thing here is that this IC does not support OVP (Over Voltage Protection) although the manufacturer states that it is present in RAPM550.


Soldering and workmanship on the main and modular PCBs are good enough for the price range of the unit.


The cooling fan is provided by Young Lin Tech, its model number is DFS132512H (12V, 0.25A, 1700RPM, 91.16 CFM, 36.28 dBA) and it uses sleeve bearing.