The electronics store chain Best Buy has several house brands and two of them are used for computer components: Dynex and Rocketfish. We have already reviewed Dynex 400 W power supply and Rocketfish 700 W power supply. While the models we reviewed a while ago were manufactured by Huntkey, Best Buy decided to hire a different company for their 550 W model: CWT. They also replaced Huntkey as the manufacturer for their 700 W model, so the 700 W model you find now on stores today (labeled “RF-700WPS2”) is manufactured by CWT, not by Huntkey anymore. Let’s see if this new 550 W power supply survives our tests.
Rocketfish 550 W (also known as RF-550WPS) is not a 550 W power supply, but a 500 W model with 550 W peak wattage. At least they put this very clear on the product box, even though we are completely against this practice. We think all power supplies should be labeled with their continuous maximum wattage at a high temperature (of at least 40° C). The reasons are clear if you follow our reviews (if you don’t click here to understand more).
Rocketfish 550 W is 6 19/64” (160 mm) deep, using a 140 mm fan that glows blue when turned on on its bottom and featuring active PFC.
The reviewed power supply has a modular cabling system with three cables coming from inside the unit and thus permanently attached to the power supply: the main motherboard cable (with a 20/24-pin connector), one cable with two ATX12V connectors that together form an EPS12V connector and one cable with one six-pin auxiliary power connector for video cards. These cables are protected by a nylon sleeving that comes from inside the power supply.
The modular cabling system has four connectors and the power supply comes with five cables:
- One auxiliary power cables for video cards with one six-pin video card auxiliary power connector (installed on the red connector from the system).
- Two SATA power cables with three SATA power connectors each.
- One peripheral power cable with three standard peripheral power plugs and one floppy disk drive power connector.
- One peripheral power cable with four standard peripheral power plugs.
The number of cables is enough for you to build a mainstream PC, but you will have trouble if you’d like to install a very high-end video card that features an eight-pin power connector, as this power supply only has six-pin connectors.
All wires are 18 AWG, which is the correct gauge to be used. All cables measure 17” (43 cm) between the power supply and the first connector on the cable, and then 5 ½” (140 mm) between each connector on the cable on cables that have more than one connector.
Now let’s take an in-depth look inside this power supply.
[nextpage title=”A Look Inside The Rocketfish 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.
This page will be an overview, and then in the following pages we will discuss in detail the quality and ratings of the components used.
[nextpage title=”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.
The transient filtering stage from this power supply is very simple but carries all recommended components, plus two extra Y capacitors and one extra X capacitor. The MOV is located on the right side of the right coil in Figure 8, covered by a black rubber protection.
In the next page we will have a more detailed discussion about the components used in the Rocketfish 550 W.
[nextpage title=”Primary Analysis”]
On this page we will take an in-depth look at the primary stage of Rocketfish 550 W. For a better understanding, please read our Anatomy of Switching Power Supplies tutorial.
This power supply uses one KBU10J rectifying bridge in its primary, which can deliver up to 10 A at 75° C. This component is clearly overspec’ed: at 115 V this unit would be able to pull up to 1,150 W from the power grid; assuming 80% efficiency, the bridge would allow this unit to deliver up to 920 W without burning t
his component. Of course we are only talking about this component and the real limit will depend on all other components from the power supply.
On the active PFC circuit two FCPF20N60 power MOSFET transistors are used, each one capable of delivering up to 20 A at 25° C or 12.5 A at 100° C in continuous mode (note the difference temperature makes), or up to 60 A in pulse mode at 25° C. These transistors present a resistance of 150 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.
This power supply uses a Japanese capacitor from Chemi-Con labeled at 85° C to filter the output from the active PFC circuit.
In the switching section, another two FCPF20N60 power MOSFET transistors are used on the traditional two-transistor forward configuration. The specs for these transistors we already published above.
The primary is controlled by the “famous” CM6800 PFC/PWM combo controller.
Now let’s take a look at the secondary of this power supply.
[nextpage title=”Secondary Analysis”]
This power supply uses four Schottky rectifiers on its secondary.
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%.
The +12 V output is produced by two SBR30A60CT (30 A, 15 A per internal diode at 110° C, typical voltage drop of 0.53 V) connected in parallel. This gives us a maximum theoretical current of 43 A or 514 W for the +12 V output.
By the way, we are now talking about the voltage drop presented by the rectifiers. This parameter shows how much voltage is wasted by the rectifier. The lower this number is, the better, as less voltage is wasted, increasing efficiency.
The +5 V output is produced by one STPS30L30CT Schottky rectifier (30 A, 15 A per internal diode at 140° C, maximum voltage drop of 0.57 V), giving us a maximum theoretical current of 21 A or 107 W for this output.
The +3.3 V output is produced by one STPS3045CW Schottky rectifier (30 A, 15 A per internal diode at 155° C, maximum voltage drop of 0.57 V), giving us a maximum theoretical current of 21 A or 71 W for this output.
All these numbers are theoretical. The real amount of current/power each output can deliver is limited by other components, especially by the coils used on each output.
The outputs are monitored by an SG6516DZ integrated circuit, which supports under voltage (UVP), over voltage (OVP) and over current (OCP) protections. Any other protection that this unit may have is implemented outside this integrated circuit.
Most electrolytic capacitors from the secondary are Japanese from Chemi-Con, but some of them are Chinese from Samxon.[nextpage title=”Power Distribution”]
In Figure 15, you can see the power supply label containing all the power specs.
This power supply has two virtual rails, distributed like this:
- +12V1 (solid yellow wire): All cables but the ATX12V/EPS12V cable.
- +12V2 (yellow with black stripe wire): ATX12V/EPS12V connectors.
This is a somewhat adequate distribution for a power supply with two rails.
Now let’s see if this power supply can really deliver 550 W.[nextpage title=”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.
For our tests we assumed this power supply a being a 500 W model. Then we added a sixth load pattern with a 550 W load, to see if this unit could really deliver 550 W or not.
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 our tests the +12V1 input was connected to the power supply +12V1 rail and the +12V2 input was connected to the power supply +12V2 rail.
|Input||Test 1||Test 2||Test 3||Test 4||Test 5||Test 6|
|+12V1||4 A (48 W)||7 A (84 W)||11 A (132 W)||14.5 A (174 W)||18 A (216 W)||20 A (240 W)|
|+12V2||3 A (36 W)||7 A (84 W)||10 A (120 W)||14 A (168 W)||18 A (216 W)||19 A (228 W)|
|+5V||1 A (5 W)||2 A (10 W)||4 A (20 W)||5 A (25 W)||6 A (30 W)||8 A (40 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)||8 A (26.4 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)||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)||0.5 A (6 W)|
|Total||104.2 W||196.0 W||298.6 W||396.2 W||492.3 W||545.1 W|
|% Max Load||20.8%||39.2%||59.7%||79.2%||98.5%||109.0%|
|Room Temp.||45.8° C||46.5° C||45.9° C||48.3° C||46.2° C||46.5° C|
|PSU Temp.||44.9° C||45.9° C||44.2° C||47.1° C||47.3° C||47.1° C|
|Ripple and Noise||Pass||Pass||Pass||Pass||Pass||Pass|
|AC Power||122.2 W||229.3 W||351.6 W||476.5 W||609.0 W||681.0 W|
|AC Voltage||112.5 V||110.1 V||110.6 V||107.9 V||106.2 V||106.4 V|
When we tried to pull more than 500 W the power supply would shut down after a few seconds, showing that it is really a 500 W product. On the good side, it protections entered in action and we didn’t burn or explode this unit while trying to pull more than it is capable of delivering.
So for all practical effects we must consider this a 500 W unit.
Rocketfish 550 W presents an outstanding efficiency of 85% if you pull up to 300 W from it – which is what most people buying this unit will be pulling anyway. Pulling around 400 W efficiency was still pretty decent at 83%. At 500 W, however, efficiency dropped to 80.8%, still above the 80% mark.
Voltage stability is another highlight from this product. All voltages were within 3% from their nominal value, whereas the ATX specification says they must be within 5%. Translation: voltages were closer to their nominal values than needed. This includes the -12 V output, which usually likes to stay outside this range.
Ripple and noise were very low. With this power supply delivering 500 W noise level at +12 V outputs were less than half the maximum allowed. Noise on +3.3 V was very low while noise on +5 V was super low. You can see the results for test number five below. All numbers are peak-to-peak figures and the maximum allowed is 120 mV for the +12 V outputs and 50 mV for the +3.3 V and +5 V outputs.
Over current protection was present and active. The power supply wouldn’t turn on if we tried to pull more than 26 A from any one of its two rails.
[nextpage title=”Main Specifications”]
Rocketfish 550 W power supply specs include:
- ATX12V 2.3
- Nominal labeled power: 500 W continuous, 550 W peak.
- Measured maximum power: 492.3 W at 46.2° C.
- Labeled efficiency: 80% minimum
- Measured efficiency: Between 80.8% and 85.5% at 115 V (nominal, see complete results for actual voltage).
- Active PFC: Yes.
- Modular Cabling System: Yes.
- Motherboard Power Connectors: One 24-pin connector and two ATX12V connectors that together form an EPS12V connector.
- Video Card Power Connectors: Two six-pin connectors.
- Peripheral Power Connectors: Seven in two cables.
- Floppy Disk Drive Power Connectors: One.
- SATA Power Connectors: Six in two cables.
- Protections: Information not available. Over current (OCP) and short-circuit (SCP) protections (SCP) present and working.
- Warranty: One year.
- More Information: https://www.bestbuy.com
- Price in the US: USD 89.99.
We must say that we were really impressed by this new Rocketfish power supply. Although it is not really a 550 W unit, it is a decent 500 W power supply and available for a not so bad price (USD 90 on any Best Buy store), which is unique, as Best Buy is certainly not know for having the best prices around. Of course it could cost less, but the advantage of this unit is that you can find it on any Best Buy and may be a good buy when you need a decent power supply over the weekend and/or can’t wait for the delivery from your favorite on-line store.
Rocketfish achieved a high 85% efficiency when we pulled up to 300 W, which is more than anyone thinking of buying this unit will pull anyway.
The only drawback from this unit is only has six-pin video card connectors. One of them should be a six/eight-pin connector in order to allow you to install one very high-end video card.
For the user building a mainstream PC, this power supply is a good buy.
Be aware that Best Buy warranty is of only one year, and most brands in the US offer warranty of at least three years. This is also something you should keep in mind.
The bottom line: it passed our tests.