Scythe Kamariki 4 550 W Power Supply Review
By Gabriel Torres on July 17, 2009


Introduction

Hardware Secrets Golden Award

Scythe, a Japanese manufacturer known for its high-end CPU coolers, also has power supplies. Their latest power supply series is called Kamariki 4 and has 450 W, 550 W, 650 W and 750 W models and we are going to review the 550 W version, also known as KMRK4-550A. Let’s see if it will live up to our expectations.

This power supply series is currently available only in Europe and Japan (the 750 W model is available only in Japan) and we believe Scythe will bring them to the USA very soon.

By the way, “kamariki” means “power of the sickle” in Japanese, and Scythe’s logo has two sickles.

We couldn’t find out the real manufacturer behind the reviewed power supply, however we know that other series from Scythe are manufactured by Topower (a reader says this unit is manyfactured by Sirtec).

Scythe Kamariki 4 550 W power supply
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Figure 1: Scythe Kamariki 4 550 W power supply.

Scythe Kamariki 4 550 W power supply
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Figure 2: Scythe Kamariki 4 550 W power supply.

Scythe Kamariki 4 550 W is 6 19/64” (160 mm) deep, has a small 100-mm fan on its bottom (this is the first time we’ve seen a power supply using this size of fan) and active PFC, of course. What is really unique about this power supply is the presence of three connectors for external fans, as you can see in Figure 2. Thus you can connect up to three fans available on your case to be controlled by the power supply thermal circuit, which changes the speed of the fans according to the temperature of the power supply secondary heatsink. The unit comes with three cables for you to extend the length of the cables from your fans, so you won’t have any problem connecting a fan that is far away from the power supply to one of the available power connectors.

Kamariki 4 doesn’t have a modular cabling system. All cables are protected with nylon sleevings, but only the one used on the main motherboard cable come from inside the unit, as you can see in Figure 2.

The cables included are:

All cables are relatively long for a 550 W product, measuring 20” (51 cm) between the power supply housing and the first connector on the cable (the fan extender cables are also 20”/51 cm in  length). On cables with more than one connector there is 6 19/64” (160 mm) between the plugs, a little bit more distant than usual, which is great.

All wires are 18 AWG, which is the correct gauge to be used. The number of cables is enough for building a mainstream PC with one very high-end video card or two mainstream video cards. The highlight here is the high number of SATA power plugs (eight).

Scythe Kamariki 4 550 W power supply
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Figure 3: Cables.

Now let’s take an in-depth look inside this power supply.

A Look Inside The Kamariki 4 550 W

We decided to disassemble this power supply to see what it looks like inside, how it is designed, and what components are used. Please read our Anatomy of Switching Power Supplies tutorial to understand how a power supply works and to compare this power supply to others.

Scythe Kamariki 4 550 W power supply
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Figure 4: Overall look.

Scythe Kamariki 4 550 W power supply
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Figure 5: Overall look.

Scythe Kamariki 4 550 W power supply
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Figure 6: Overall look.

Transient Filtering Stage

As we have mentioned in other articles and reviews, the first place we look when opening a power supply for a hint about its quality, is its filtering stage. The recommended components for this stage are two ferrite coils, two ceramic capacitors (Y capacitors, usually blue), one metalized polyester capacitor (X capacitor), and one MOV (Metal-Oxide Varistor). Very low-end power supplies use fewer components, usually removing the MOV and the first coil.

This power supply is flawless on this stage, having one X capacitor and two Y capacitors more than required.

Scythe Kamariki 4 550 W power supply
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Figure 7: Transient filtering stage (part 1).

Scythe Kamariki 4 550 W power supply
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Figure 8: Transient filtering stage (part 2).

In the next page we will have a more detailed discussion about the components used in the Scythe Kamariki 4 550 W.

Primary Analysis

On this page we will take an in-depth look at the primary stage of Scythe Kamariki 4 550 W. For a better understanding, please read our Anatomy of Switching Power Supplies tutorial.

This power supply uses one GBU805 rectifying bridge in its primary, which can deliver up to 8 A at 100° C. At 115 V this unit would be able to pull up to 920 W from the power grid; assuming 80% efficiency, the bridge would allow this unit to deliver up to 736 W without burning this component. Of course we are only talking about this component and the real limit will depend on all other components from the power supply.

Scythe Kamariki 4 550 W uses two SPP20N60C3 power MOSFET transistors on its active PFC circuit, each one capable of delivering up to 20.7 A at 25° C or 13.1 A at 100° C in continuous mode (note the difference temperature makes) or up to 62.1 A at 25° C in pulse mode, presenting a resistance of 160 mΩ when turned on, a characteristic called RDS(on). This number indicates the amount of power that is wasted, so the lower this number the better, as less power will be wasted thus increasing efficiency.

Scythe Kamariki 4 550 W power supply
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Figure 9: Rectifying bridge, active PFC transistors and diode.

The electrolytic capacitor in charge of filtering the active PFC output is Japanese from Chemi-Con and labeled at 105° C. This is great for two reasons. First Japanese capacitors have the best quality and don’t suffer from leakage and second it is better to see caps labeled at 105° C instead of 85° C.

This power supply uses another two SPP20N60C3 power MOSFET transistors on the traditional two-transistor forward configuration on its switching section. The specs for these transistors are published above.

Scythe Kamariki 4 550 W power supply
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Figure 10: Switching transistors.

The primary is controlled by a FAN4800I PFC/PWM controller.

Scythe Kamariki 4 550 W power supply
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Figure 11: PFC/PWM controller.

Secondary Analysis

Scythe Kamariki 4 550 W has six Schottky rectifiers on its secondary, all from the same model: ESAD83-004R. Each one is capable of handling up to 30 A (15 A per internal diode at 118° C, maximum voltage drop of 0.55 V).

The maximum theoretical current each line can deliver is given by the formula I / (1 - D), where D is the duty cycle used and I is the maximum current supported by the rectifying diode. Just as an exercise, we can assume a typical duty cycle of 30%.

Each main positive output is produced by two of those rectifiers connected in parallel, giving a maximum theoretical current of 43 A for each output, what translated into a maximum theoretical power of 514 W for the +12 V output, 214 W for the +5 V output and 141 W for the +3.3 V output. It is always good to remember that the real current/power limit for each output will depend on other factors, especially on the coils used.

Scythe Kamariki 4 550 W power supply
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Figure 12: Rectifiers.

This power supply uses a PS224 monitoring integrated circuit, which supports over voltage (OVP), under voltage (UVP) and over current (OCP) protections.

Scythe Kamariki 4 550 W power supply
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Figure 13: Monitoring integrated circuit.

All the electrolytic capacitors from the secondary are Taiwanese from a company called TREC (Transcend Electrolytic Co) and labeled at 105° C, as usual. We think Scythe could use only Japanese caps.

Power Distribution

In Figure 14, you can see the power supply label containing all the power specs.

Scythe Kamariki 4 550 W power supply
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Figure 14: Power supply label.

This power supply features two +12 V virtual rails distributed like this:

This is the standard distribution for a two-rail power supply.

Now let’s see if this power supply can really deliver 550 W.

Load Tests

We conducted several tests with this power supply, as described in the article Hardware Secrets Power Supply Test Methodology.

First we tested this power supply with five different load patterns, trying to pull around 20%, 40%, 60%, 80%, and 100% of its labeled maximum capacity (actual percentage used listed under “% Max Load”), watching how the reviewed unit behaved under each load. In the table below we list the load patterns we used and the results for each load.

If you add all the power listed for each test, you may find a different value than what is posted under “Total” below. Since each output can vary slightly (e.g., the +5 V output working at +5.10 V), the actual total amount of power being delivered is slightly different than the calculated value. On the “Total” row we are using the real amount of power being delivered, as measured by our load tester.

+12V1 and +12V2 are the two independent +12V inputs from our load tester and during out tests the +12V1 input was connected to the power supply +12V1 rail and +12V2 input was connected to the power supply +12V2 rail.

Input

Test 1

Test 2

Test 3

Test 4

Test 5

+12V1

4 A (48 W)

8 A (96 W)

12 A (144 W)

16 A (192 W)

20 A (240 W)

+12V2

4 A (48 W)

8 A (96 W)

12 A (144 W)

16 A (192 W)

20 A (240 W)

+5V

1 A (5 W)

2 A (10 W)

4 A (20 W)

5 A (25 W)

6 A (30 W)

+3.3 V

1 A (3.3 W)

2 A (6.6 W)

4 A (13.2 W)

5 A (16.5 W)

6 A (19.8 W)

+5VSB

1 A (5 W)

1 A (5 W)

1.5 A (7.5 W)

2 A (10 W)

2.5 A (12.5 W)

-12 V

0.5 A (6 W)

0.5 A (6 W)

0.5 A (6 W)

0.5 A (6 W)

0.5 A (6 W)

Total

116.3 W

220.8 W

335.8 W

439.9 W

542.6 W

% Max Load

21.1%

40.1%

61.1%

80.0%

98.7%

Room Temp.

46.2° C

44.9° C

46.5° C

47.6° C

45.1° C

PSU Temp.

50.9° C

51.0° C

50.6° C

52.0° C

54.4° C

Voltage Stability

Pass

Pass

Pass

Pass

Pass

Ripple and Noise

Pass

Pass

Pass

Pass

Pass

AC Power

145.1 W

265.0 W

403.5 W

536.4 W

677.0 W

Efficiency

80.2%

83.3%

83.2%

82.0%

80.1%

AC Voltage

113.3 V

112.7 V

110.8 V

110.3 V

107.3 V

Power Factor

0.927

0.965

0.981

0.988

0.991

Final Result

Pass

Pass

Pass

Pass

Pass

Scythe Kamariki 4 550 W can really deliver its labeled power at 45° C, which is great.

Efficiency was good, but not spectacular. Typically between 82% and 83% makes Kamariki 4 to be a decent but not outstanding product. At light load (20% load, i.e.,  110 W) and full load (550 W) efficiency was at 80%.

Voltage stability was the highlight of this product, with all of them (including the -12 V output, which usually don’t like to stay close to its nominal voltage) within 3% of their nominal values. Translation: voltages closer to their nominal value than demanded by the ATX specification, which gives a 5% tolerance for all outputs (10% for -12 V).

Ripple and noise levels were low. Below you can see the screenshots from test number five, with this power supply delivering 550 W. Just to remember, the maximum allowed for the +12 V outputs is 120 mV and the maximum allowed for the +5 V and +3.3 V outputs is 50 mV. All these values are peak-to-peak figures.  

Scythe Kamariki 4 550 W power supply
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Figure 15: +12V1 input from load tester at 542.6 W (58.6 mV).

Scythe Kamariki 4 550 W power supply
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Figure 16: +12V2 input from load tester at 548.6 W (58.6 mV).

Scythe Kamariki 4 550 W power supply
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Figure 17: +5V rail with power supply delivering 548.6 W (34.8 mV).

Scythe Kamariki 4 550 W power supply
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Figure 18: +3.3 V rail with power supply delivering 548.6 W (31.4 mV).

Even though this won’t make any difference for the user, notice how power factor was at 0.927 during test one, and usually power supplies with active PFC present a power factor of at least 0.98.

Now let’s see if we could pull even more power from Kamariki 4 550 W.

Overload Tests

Before overloading power supplies we always test first if the over current protection (OCP) circuit is active and at what level it is configured. We increased current on +12V2 up to 33 A (the maximum supported by our load tester) and the power supply didn’t shut down, meaning that the unit either doesn’t have an OCP circuit or it is configured at a value above 33 A (according to the manufacturer OCP is configured at 40 A on each +12 V rail and that's why we couldn't see it in action).

Starting from test five we started overloading the power supply. Below you can see the maximum amount of power we could pull with it still working inside ATX specs. We only stopped overloading it because noise on -12 V was above the maximum allowed (120 mV) when we increased on more amp from any output.

The goal from our overloading test is to see if the power supply will burn or explode if you try to pull more than its labeled power. This didn’t happen with Kamariki 4 and in fact we could pull 46% above its labeled power, which is remarkable, as power supplies usually allow us to overload them somewhere between 15% and 25% from their labeled wattage. Notice, however, how efficiency was low under this extreme configuration.

Input

Maximum

+12V1

25 A (300 W)

+12V2

25 A (300 W)

+5V

10 A (50 W)

+3.3 V

10 A (33 W)

+5VSB

2.5 A (12.5 W)

-12 V

0.5 A (6 W)

Total

731.4 W

% Max Load

146.3%

Room Temp.

45.7° C

PSU Temp.

56.4° C

AC Power

961.0 W

Efficiency

76.1%

AC Voltage

100.9 V

Power Factor

0.997

Main Specifications

Scythe Kamariki 4 550 W power supply specs include:

Conclusions

Scythe Kamariki 4 550 W is a good power supply. It can really deliver 550 W at 45° C and during our tests we could pull up to 731 W from it. Efficiency was between 82% and 83% when we pulled between 40% and 80% from its labeled capacity (between 220 W and 440 W) and noise level was always relatively low.

It will please the average user looking for a good mainstream unit, as it provides eight SATA power connectors and two six/eight-pin video card auxiliary power connectors, plus the ability to control the speed of fans located inside the case depending on the power supply internal temperature.

In summary, it is a good but not outstanding power supply, being an honest product that will get the job done. Its success will mainly depend on the price tag it will reach the market.

Originally at http://www.hardwaresecrets.com/article/Scythe-Kamariki-4-550-W-Power-Supply-Review/762


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