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Silverstone Zeus ST85ZF 850W Power Supply Review

Cases & PSU/Power Supplies by KeithSuppe @ 2007-01-11

Silverstone Technology Ltd. is a relative newcomer to the PC-world having been founded in 2003. As a manufacturer of power supplies, CPU-coolers and enclosures they aggressively sought to compete with the very best in these product categories. Over the last year they have come into their own with the release of the well received Temjin TJ06 aluminum case and Zeus line of PSUs. Silverstone is now a relatively familiar name and we have the flagship of the Zeus series, the ST85ZF.

Circuit topology, Primary PCB

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.

Madshrimps (c)

Silverstone 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.

Madshrimps (c)

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.

Madshrimps (c)

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).

Madshrimps (c)

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.

Madshrimps (c)

Onto the Secondary PCB -->

Comment from Sidney @ 2007/01/11

Quote:

From Hardware Secrets; Why 99% of Power Supply Reviews Are Wrong. I'm sure that article will have a substantial impact on most PSU reviews you have read.

I've read the article the day it came out, and found the statement rather inaccurate. A Chroma station, measuring amp and or wattage or voltage by replicating the manufacturer QC station process, and even taking IQC (incoming QC on purchased components) are for the engineering professional in electrical field. When I test drive a car, I only need to know how it responses, sitting/driving position, steering inputs, acceleration (if it is important to me), gas mileage (if it is labled for good mileage consumption), price point and the "look", etc, etc ...... One thing I don't mind not knowing is all the engine, chassis, suspension, gear-box design and specifications (although some of us do want to know because we are very good at it).

99% of reviews are wrong sounded is a bit odd. It depends on the type of audience; 99% are electrical engineers (by formal training or otherwise) and PC enthusiasts; leaving 1% reader who asks that give me a power supply that fits well in my case and support my system without over kill in paying for something I don't need is a strange statement.

By the way, the article serves me well

Comment from EsaT @ 2007/01/19

I just checked article more closely and I think you are wrong about 12V rails being really separate.

Basing to these pics looks much like at least 1 and 2 are "jumpered" (those thick metal jumpers) from same trace.
And basing to bottom side of PCB also 3 and 4 are propably similarly connected.

In fact looks like all 12V rails are directly connected to each other after those "jumpers", PCB traces seem to connect to each others on left edge of pic.

Quote:

Originally Posted by lazyman

When I test drive a car, I only need to know how it responses...

99% of reviews are wrong sounded is a bit odd.

So you test drive car using just gear 1?
Or more precisely without any driving and seeing just that engine works at idle?

Comment from jmke @ 2007/01/19

rather testing driving the car on race roads, normal roads, traffic jams, long distances, short distances, parking, booth space, easy maintenance, wheel removal kit, seat arrangements, mirror placement, etc etc

you don't need to know how the engine works to make an evaluation of how the car drives

knowing how the engine works can help to explain why the car drives as it does, but it's not a necessary ingredient to make a good evaluation of the car, of course, cars and PSU are not quite a like, and comparo here might not be appropriate

Comment from Sidney @ 2007/01/19

If it is automatic trans; most people don't just put it in "D"; drive away

If it is humming along quietly, most drivers don't care how it works

I am referring to majority of drivers.

Comment from EsaT @ 2007/01/19

Quote:

Originally Posted by lazyman

I am referring to majority of drivers.

But most people propably wouldn't trust test drive of car done by using only gear 1, that's what that majority of PSU reviews with barely 1/3 of load specified in ads of PSU are...

On the other hand this specie might have once again digged deeper than previously reached level of rock bottom.

Comment from Sidney @ 2007/01/20

You don't buy a car just by reading test report I hope

Comment from jmke @ 2007/01/20

it does help make the decision a lot, testing driving PSU is hard

Comment from Sidney @ 2007/01/20

My initial post was related to the 99% reviews being wrong. Here is my take-
1) A car is rated to have 500HP rear or front wheel power; top speed 180MPH. There will be manufacturing variables, and a dyno test may or may not prove 100% accurate. Now comes the 180mph test, again there are many variables plus having a track to do the test against normal traffic. A test drive reviewed at 120 MPH without the track to top out is not 100% wrong. It merely ran out of track on this part of the review.
2) Since PSU is not regulated by any government (unlike cars) rating except UL for safety. It is highly dependable on the manufacturer's ablility to hold certain professional standards such as ISO which I strongly recommend consumers to look into.
3) The use of any test equipment not regularly certified does not mean much to me.

Lastly, PSU tested even at 100% spec on bench using Chroma station at a given time does not gurantee real life performance against weather condition and irregular or variable input voltage (from the wall or motherboard). Look for solid and reputable manufacturer or name brand; reading test reports include cable length, flexibility, size to fit most or just certain cases, and noise level; to say 99% of reviews are wrong because they might not test the max output is "odd".

We could go another step to look into component specs +/- 3%? Or requesting BOM (bills of material) and supplier listings?

Comment from Liquid3D @ 2007/01/25

I actually re-evaluatewd that article myself. I also found several points which were inconsistent. I wasn't trying so much to discredit our or any other methodologies as I was trying to challange those sites whom feel their tests are beyond reproach. Many of the top test sites with the very best hardware use voltage regulation as a standard test.

When you think of it, since all PSU's have voltage regulation it's not as if their testing the PSU's "power reserve" their actually measuring (if it's possible) the unit's ability to compensate for Rail fluctuation. Without "true" independent voltage regulation fluctuation will be regulated, often at the xpense of theo others Rails. Therefore measuring rail stability may only show one or two phenomenon: First - time it takes to compensate (get the rail back to "spec". Second - wether or not PSU is able to compensate without any affecting other rails or circuits in the design. The paper states the latter is almost impossible because one would need to monitor all rails simultaneously.

IMHO it's not so much the rail in question is immedately regulated, but more importantly this regulation is proprietary as is the current source behind it.

For exmaple if 12V3 dips and it is compensated for, does this now effect 12V1, 12V2 and 12V4? While independent voltage regulation may avoid any impact on other rails, much more important to me is where that power comes from?

The jumpers you refer do not seem to connect any of the 12V rails on the face of it, but I'll follow the traces to be sure if you like?

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