PCB Layout, Dual Design
Madshrimps has seen numerous Silverstone products on our test benches and one of our most experienced reviewers Piotke
, recently tested the sibling to the ST85ZF in his Silverstone ST75ZF review
. Both the Zeus ST75ZF
and ST85ZF are very close in their specifications and seem to contain identical parts. Insofar as amperes supplied on the ST75ZF’s 12V-Rail, the sibling to the model reviewed here offers 60A. The ST85ZF produces 70A on the combined 12V rails. S
ilverstone collaborated with Etasis
(perhaps even Enhance Electronics
) to build their ST85ZF. The design is based on the Etasis EPAP-850
, however; disassembling the unit created quite the identity conundrum. We will delve deeper into this identity crisis on Page 5. Below after disassembling the unit, we see the primary (left) and secondary (right) circuit boards side by side. The layout is well organized if somewhat complicated.
Beginning with the primary PCB; the board contains transient filtering stages, active PFC (Power Factor Correction), and rectification. The primary board also accommodates a pair of Hitachi 390uf/420v high voltage electrolytic capacitors which store then smooth AC current. We also find various inductors, an Xtra capacitor (bottom right yellow "box") and a transformer just above the rectifier heatsink on the far left.
Silverstone incorporated extensive filtering on the ST85ZF; including a Delta transient filter at the AC-input (thumbnails below). From this filter, current travels to the primary where a quick connect is necessary in this dual PCB construction. Surrounding the connector we find a fuse marked 12A/250V, transient filtering, surge suppression and a series of coils (or inductors) leading to the rectifying bridge. As I am only just beginning to comprehend power supply circuitry I am hypothesizing that the only transformer found on the primary PCB pertains to the active PFC stage (right thumbnail).
Below we take a closer look at the PFC circuitry which utilizes a Texas Instruments UC3818D
power factor pre-regulator chip (left thumbnail). The second thumbnail (right) features a close-up of the active PFC transformer bearing the part number EPAP-750. A benefit to active PFC is that there is no longer a need for a manual 220V /120V AC switch
Onto the Secondary PCB -->