Disassembly
The input filtering consists of two X capacitors, five Y capacitors (one after the rectifier), two common-mode chokes and two MOVs, which is plenty of components. Most of them are installed on a separate PCB. The voltage doubler section employs an 8A bridge rectifier and two 680µF capacitors supplied by Teapo. It is noteworthy, however, that some HP-D3057F3H power supplies we have come across over the years use Japanese Panasonic capacitors in this position. The switching transistor on this unit is a Toshiba 2SK2611 MOSFET, which is rated for 9A at 25°C with an RDS(on) of 1.2Ω. Interestingly, the other unit tested here had a Fairchild FQAF11N90C; this FET is only rated for 7A at 25°C, but has a typical RDS(on) of 0.91Ω – 24% lower than the 2SK2611. This means that, although this unit’s switcher is rated for slightly more current, it may have been running as much as 32% hotter, which could explain why it failed at a lower load (since both were rated for the same maximum temperature). Note the resistor which was also burned in the explosion in the above right picture. The 5Vsb section uses a switching IC instead of a two-transistor circuit. The part used is an ST VIPer22A.
This particular unit uses Teapo SC series capacitors throughout the secondary side. I have seen other HP-D3057F3H power supplies with various combinations of Teapo, LTEC, Nichicon and Nippon Chemi-con parts. The power supplies which come with Teapo and LTEC capacitors rarely last longer than three to four years with moderate use. It seems that the cheaper Taiwanese capacitors simply cannot handle the stresses which these power supplies put on them.
The 12V rail uses two NXP Semiconductors BYQ30E-200 Ultra-fast recovery rectifiers which are rated at 16A each. The 5V rail uses two STPS30L60CT Schottky rectifiers, rated at 30A each, and the 3.3V rail uses a Lite-On SBL2060CT Schottky rectifier, rated at 20A. These rectifiers are all good enough for what the label claims about the rails. However, the use of fast recovery rectifiers on the 12V rail, as opposed to Schottky rectifiers, would have contributed to the poor efficiency results we saw in the load testing. The use of 60V rated rectifiers (which have higher forward voltage drops than their 45V or lower rated counterparts) on the lower voltage rails, with no visible justification, doesn’t improve matters. The controller IC is a Texas Instruments TPS3514N. It supports Over Current Protection on one 12V rail, which is all that this power supply is advertised as having.
The soldering was generally not too bad, but there were a few issues. The first problem I noticed was around where the fan wires are soldered in. Both the ends of the wires and one other component pin were left too long, and there was some excess flux from the soldering which wasn’t cleaned off. There was also one joint on a surface mounted resistor near the rectifiers which had way too much solder on it.
The fan is a Cheng Home Electronic (Superred) CHA8012C series. This is a sleeve bearing part with speed, airflow and noise ratings of 3000RPM, 37.9CFM and 34.6dB respectively. It first became quite noticeable in Test 5, with the PSU loaded to around 250W. It was never disturbingly loud, though. Unfortunately, the bearing is completely dry, with no oil or lubricant visible – not good for the longevity of the fan. This has also been the case with every one of these power supplies I have disassembled. The heatsinks are massive. They are extremely thick and have good amount of surface area, which is why the fan doesn’t have to run particularly fast.
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