Dis-assembly
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The HX750’s input filtering starts at the AC receptacle, with an X-Capacitor and two Y-capacitors. The main PCB contains two coils, another X-Capacitor, two Y-Capacitors and an MOV. All up, that’s more than enough components for the job. The Active PFC section uses two Infineon SPW20N60C3 MOSFETs rated at 20A each, and two 330µF capacitors made by Nippon Chemi-con. The switching transistors are IRFP460A MOSFETs rated at 20A each. Everything is controlled by a Champion Micro CM6802 PFC/PWM controller combo.
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The secondary side capacitors are all Nippon Chemi-con KZE and KY series, which are very reliable Japanese parts. The 5V and 3.3V VRMs use Solid Polymer capacitors from Nichicon and Chemi-con.
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The 12V rail uses transistors for the rectification, as opposed to diodes. Three Infineon IPP037N08N3 MOSFETS handle the the main rectification. They are rated for 100A each, which means that the 12V rail is perfectly capable of 300A. Overkill much? Two 120A STP160N75F3 MOSFETS are used to discharge the coils (also known as freewheeling). The 5V and 3.3V rails use DC-DC conversion from the 12V rail, so some of the 12V’s output current has to be shared with them. The VRMs use three Infineon IPD060N03LG MOSFETs rated at 50A each, so the 5 and 3.3V rails are capable of up to 150A each.
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The soldering isn’t too bad, but there are a few joints on small surface mounted components which could have been done better, like in the above right picture. Another problem is with the screws on the heat sink with the PFC transistors. They are done up so loose that I can do them up tighter with my bare fingers. There is no thread lock used either. I also found a solder crumb stuck in the glue on one of the DC-DC VRMs. If there’s one area where CWT could really improve their quality, it’s the soldering.
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The fan is a 140mm Ball bearing part made by Yate Loon. This model spins at 2800RPM and moves 140CFM of air with a noise rating of 48.5dB. The heat sinks are just slabs, and have no fins. Generally, I’m not a big fan of fin-less heat sinks, since they have much poorer surface-to-air contact than heat sinks with fins, but very efficient power supplies don’t generate a lot of heat. As an experiment, I opened this power supply just minutes after shutting it down after the overload test, and they actually felt a lot cooler than they do on most PSUs.
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