Rosewill Tachyon 650W Power Supply Review

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A look inside the Tachyon 650W

The cooling fan

The 140mm fan inside the Tachyon 650W power supply has been rebranded by Rosewill but from the part number we identified it as the RL4Z S1402512HH fan by Globe, a rather rare fan with a sleeve bearing and a very high top speed. The S1402512HH can go as fast as 1800RPM, an extremely high speed for a 140mm fan, which is why the selection of this particular model for the cooling of an 80Plus Platinum unit is a very peculiar choice.

Inside the Rosewill Tachyon 650W unit

Rosewill chose Super Flower Computer Inc to be the OEM behind the 650W version of the Tachyon. Super flower is a reputable Taiwanese designer and manufacturer of computer power supplies and also is the OEM behind most of Rosewill’s PSUs today. The very design of the Tachyon 650W unit is an upgraded version of the platform we encountered in the Capstone 750W a few months ago, allowing it to achieve 80Plus Platinum efficiency levels and greater overall performance.

The filtering and rectifying stages

The filtering stage of this power supply starts directly on the PCB, without any parts at the back of the A/C cable receptacle. On the PCB however there were four Y capacitors, three X capacitors and two filtering chokes. Although these are more parts than required for a standard transient filter, we were unable to locate a MOV. Metal Oxide Varistors (MOVs) are being used for surge suppression, the functions of which have been largely replaced by the active PFC circuits; however, this could still indicate that this unit’s tolerance against lighting and or switching surges is limited.

Primary side

We found the primary rectifying bridge attached on an extended portion of the large heatsink holding the active PFC transistors and the two switching inversion transistors which form a resonant half-bridge configuration. A Nippon Chemi-Con 470um/400V 105°C capacitor takes care of the APFC filtering.

Secondary side

The large heatsink on the secondary side holds the rectifying transistors which generate the 12V rail. The minor rails are being derived from the 12V rail via DC to DC conversion circuits, found on a daughterboard right next to the heatsink. The metallic shields over the DC to DC conversion circuit transistors are to block interference and assist in cooling. The electrolytic capacitors on the secondary side are provided by Nippon Chemi-Con as well. 

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