Rosewill Capstone 750W Power Supply Review

A look inside the Rosewill Capstone 750W

The 140mm fan inside the Capstone
750W unit has been rebranded by Rosewill but from the part number we could
instantly identify it as the RL4ZB1402512M fan by Globe, a product commonly
found cooling middle-range power supply units. It is a slow 1200RPM model with
a long life ball bearing engine.

Even though the Capstone 750W looks
almost like a simple generic power supply, cranking it open revealed that the
OEM behind this product is Super Flower Computer Inc, one of the most reputable
Taiwanese designers of power supplies. The internal quality and craftsmanship
is well above average, exactly what an enthusiast would expect from such a
manufacturer. It is also interesting to note that this design was clearly meant
for modular units, as the excessive clearance towards the back of the unit is
obviously meant for a vertical PCB holding the modular connectors.

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.

A large Nippon Chemi-Con 560um/400V
105C capacitor is present at the primary side of the unit, next to a massive PFC
choke. The two transistors and the diode forming the APFC circuit as well as
the primary side pair of power transistors forming the LC resonant converter
have all been placed on a single long heatsink.

The transistors of the synchronous
rectifier can be found on the smaller black heatsink and the DC to DC
conversion circuits are present on the large vertical board on the secondary
side of the unit. All of the secondary side capacitors, electrolytic and
polymer alike, are made by Nippon Chemi-Con as well.