A Look Inside
The input filtering starts at the AC inlet. Located there is an X capacitor and two Y capacitors. The main PCB adds an X capacitor, two common-mode chokes, four Y capacitors (2 after the rectifier, both on the negative side – one is near the 5Vsb transformer) and two MOVs, bringing the total number of components to two X capacitors, two coils, six Y capacitors and two MOVs. In plain English, it’s better than the minimum recommended input filtering. There are two 6A bridge rectifiers in parallel which, after de-rating to account for the non-linear current waveform, would theoretically allow the unit to draw 1104W from a 115V power grid and 2208W from a 230V power grid without damaging them – although they aren’t heatsinked so they will take somewhat less current in practice. The primary uses a single transistor forward design, but with two transistors in parallel. Note that this is not a two transistor forward design – that requires the transistors to be wired differently. The transistors used are Toshiba 2SK4115s rated at 7A each (14A between them). They are clearly good enough for the 460W claimed by the label. Unfortunately though, the markings on them are very faint and I couldn’t get the part number to show up for a photo, no matter what angle or what sort of light I tried. I didn’t see the point of including a photo of a plain black transistor, so you just have a bigger picture of the primary side as a whole. The 5Vsb transformer is driven by a Power Integrations TNY277PN.
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Now that would explain all the ripple on the two 12V rails. There’s only a single capacitor and no PI filtering coil. I’ve seen this before, and the result was the same – high ripple on the rail without the coil, although unlike most other power supplies that don’t have a coil, this one doesn’t even have PCB space for one. The soldering is fairly tidy, and there aren’t any particularly long component legs, although I have seen better.
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The 12V rails share two Diodes Inc. SBR20100CT schottky rectifiers rated at 20A each, meaning that in theory, they can deliver up to 40A between them. The 5V and 3.3V rails both use two SBR2045CT schottky rectifiers, also rated at 20A, so they can also deliver up to 40A in theory. Finally, a linear regulator is used for the −12V rail, which is what gave its rock-solid regulation. The secondary side is monitored by a Weltrend WT7527. It supports Over Current, Over Voltage and Under Voltage protections on up to two 12V rails.
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The fan is a Yate Loon D12SH-12. It’s rated for 88CFM and 40dB at 2200RPM. It is temperature controlled and is very quiet when the power supply is cool. The heat sinks are very thick and have lots of fins, although they aren’t particularly long. There is ample space to make them a bit larger, although they seem to do the job well enough as they are. The capacitors on the secondary side are from LTEC, which are similar in quality to OST and Teapo.
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