Seventeam ST-650P-AF Power Supply Review

[nextpage title=”Introduction”]

Seventeam is slowly entering the US market and ST-650P-AF is one of the power supplies from this brand that can be found here in the USA. Is it a good product? Can it deliver its labeled power? Check it out.

Seventeam P-AF and Z-AF series are internally identical, with the difference being the presence of a modular cabling system on Z-AF. So while we tested ST-650P-AF, the results are also valid for ST-650Z-AF. Both models are 80 Plus Bronze certified, meaning a minimum efficiency of 82% under light (20% i.e., 130 W) and full loads (650 W), and minimum efficiency of 85% while delivering half of the labeled wattage (i.e., 325 W). Seventeam also advertises this power supply as having Japanese capacitors inside, while we discovered that this isn’t entirely true (more on this later).

New models from SilverStone Element series (ST65EF, ST75EF and ST85EF) are in fact Seventeam P-AF power supplies. So numbers from this test can also be used for evaluating SilverStone Element ST65EF. It is very important to notice that other models from this series are manufactured by FSP and not by Seventeam.

We also have reviewed the 750 W version from P-AF series and it uses a different project; so the 750 W model is not a 650 W model with “stronger” components.

Seventeam trademark is the sticker in Engrish saying “Breakage Invalid” instead of “Warranty Void if Broken.”

Figure 1: Seventeam ST-650P-AF power supply.

Figure 2: Seventeam ST-650P-AF power supply.

ST-650P-AF is only 5 ½” (140 mm) deep, being shorter than the 750 W model, which is 6 19/64” (160 mm) deep. This was accomplished by reducing the fan size from 135 mm to 120 mm.

Only the main motherboard cable is protected by a nylon sleeving, which comes from inside the power supply housing. Cables are somewhat long, measuring 20 ½” (52 cm) between the housing and the first connector on the cable, and 5 ½” (140 mm) between connectors on cables with more than one connector. All wires are 18 AWG, which is the correct gauge to be used, except the +3.3 V (orange) wires on the main motherboard connector, which are thicker (16 AWG).

The cables included are:

• Main motherboard cable with a 24-pin connector (no 20-pin option).
• One cable with two ATX12V connectors that together form one EPS12V connector.
• Two auxiliary power cables for video cards with one six/eight-pin video card auxiliary power connector each.
• Two SATA power cables with three SATA power connectors each.
• One peripheral power cable with three standard peripheral power plugs each and one floppy disk drive power connector.

This is practically the same configuration found on ST-750P-AF. The only difference is the presence of one additional cable containing three peripheral power plugs on the 750 W model.

Figure 3: Cables.

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

[nextpage title=”A Look Inside The ST-650P-AF”]

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.

Seventeam says that this power supply has Japanese capacitors, however only the big electrolytic capacitor from the primary is Japanese (from Rubycon). All others are Chinese from Samxon. This wouldn’t be a problem if Seventeam didn’t use the word “capacitors” in the plural on the box and on their website. According to Seventeam, this was a wrong translation made from Chinese to English and the correct should be “main capacitor.”

As mentioned before, ST-650P-AF and ST-750P-AF use a different project.

Figure 4: Overall look.

Figure 5: Overall look.

Figure 6: Overall look.

[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. 

This power supply is flawless on this stage, with two Y capacitors, one X capacitor and one coil more than the minimum required, plus an X capacitor after the rectification bridge. The MOV is located behind the fuse.

Figure 7: Transient filtering stage (part 1).

Figure 8: Transient filtering stage (part 2).

In the next page we will have a more detailed discussion about the components used in the Seventeam ST-650P-AF.

[nextpage title=”Primary Analysis”]

On this page we will take an in-depth look at the primary stage of Seventeam ST-650P-AF. For a better understanding, please read our Anatomy of Switching Power Supplies tutorial.

This power supply uses one GBJ2506 rectifying bridg
e in its primary, which can deliver up to 25 A at 100° C  if a heatsink is used, which is the case. This component is clearly overspec’ed: at 115 V this unit would be able to pull up to 2,875 W from the power grid; assuming 80% efficiency, the bridge would allow this unit to deliver up to 2,300 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. This is the same component found on ST-750P-AF.

On the active PFC circuit two SPW20N60S5 power MOSFET transistors are used, each one capable of delivering up to 20 A at 25° C or 13 A at 100° C in continuous mode (note the difference temperature makes), or up to 40 A in pulse mode at 25° C. These transistors present a resistance of 190 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. These are the same transistors found on ST-750P-AF.

This power supply uses a Japanese capacitor from Rubycon labeled at 85° C to filter the output from the active PFC circuit. Although Seventeam advertises this power supply as having “Japanese capacitors,” only this capacitor is Japanese: all other are Chinese. Seventeam explained us that this was a problem of wrong translation from Chinese to English.

In the switching section, two SPW16N50C3 power MOSFET transistors are used on the traditional two-transistor forward configuration. Each one is capable of delivering up to 16 A at 25° C or 10 A at 100° C in continuous mode (note the difference temperature makes), or up to 48 A in pulse mode at 25° C. These transistors present a maximum RDS(on) of 280 mΩ. These are the same transistors used on ST-750P-AF.

Figure 9: Switching transistors, active PFC diode, active PFC transistors and rectifying bridge.

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

Figure 10: 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 (ST-750P-AF has six).

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 STPS60L45CW Schottky rectifiers, each one capable of delivering up to 60 A (30 A per internal diode at 135° C, maximum voltage drop of 0.50 V). This gives us a maximum theoretical current of 86 A or 1,029 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 KCQ60A04 Schottky rectifier (60 A, 30 A per internal diode at 83° C, maximum voltage drop of 0.58 V), giving us a maximum theoretical current of 43 A or 214 W for this output.

The +3.3 V output is produced by another KCQ60A04 Schottky rectifier, so the maximum theoretical power this output can deliver is of 141 W.

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.

Figure 11: +3.3 V, +5 V and +12 V rectifiers.

The outputs are monitored by a PS223 integrated circuit, which supports under voltage (UVP), over voltage (OVP), over current (OCP) and over temperature (OTP, not implemented on this power supply) protections. Any other protection that this unit may have is implemented outside this integrated circuit.

Figure 12: Monitoring circuit.

Electrolytic capacitors from the secondary are Chinese from Samxon and labeled at 105° C.

[nextpage title=”Power Distribution”]

In Figure 13, you can see the power supply label containing all the power specs.

Figure 13: Power supply label.

This power supply has two virtual rails, distributed like this:

• +12V1 (yellow with black stripe wire): ATX12V/EPS12V connectors and one of the video card auxiliary power cables.
• +12V2 (solid yellow wire): All other cables.

Now let’s see if this power supply can really deliver 650 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.

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 +12V2 rail and the +12V2 input was connected to the power supply +12V1 rail.

Input	Test 1	Test 2	Test 3	Test 4	Test 5
+12V1	5 A (60 W)	10 A (120 W)	15 A (180 W)	20 A (240 W)	24 A (288 W)
+12V2	5 A (60 W)	10 A (120 W)	15 A (180 W)	19 A (228 W)	24 A (288 W)
+5V	1 A (5 W)	2 A (10 W)	4 A (20 W)	6 A (30 W)	8 A (40 W)
+3.3 V	1 A (3.3 W)	2 A (6.6 W)	4 A (20 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)
-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	142.1 W	272.6 W	400.9 W	539.9 W	662.3 W
% Max Load	21.9%	41.9%	61.7%	83.1%	101.9%
Room Temp.	45.3° C	45.2° C	46.1° C	48.6° C	48.3° C
PSU Temp.	50.7° C	50.6° C	51.1° C	52.9° C	54.9° C
Voltage Stability	Pass	Pass	Pass	Pass	Pass
Ripple and Noise	Pass	Pass	Pass	Pass	Pass
AC Power	177.2 W	324.6 W	476.5 W	652.0 W	843.0 W
Efficiency	80.2%	84.0%	84.1%	82.8%	78.6%
AC Voltage	114.3 V	113.2 V	112.2 V	110.1 V	107.5 V
Power Factor	0.982	0.993	0.997	0.998	0.999
Final Result	Pass	Pass	Pass	Pass	Pass

Seventeam ST-650P-AF can really deliver its labeled wattage. The problem, however, is that efficiency was below of what we were expecting. Being an 80 Plus Bronze power supply, we were expecting it to present 82% minimum efficiency at light load (20% load, i.e., 130 W) and full load (i.e., 650 W), but this didn’t happen. The reason is that we test power supplies at a room temperature that is double of used by the 80 Plus certification, and the higher temperature the lower efficiency is. We’ve already explained this in more details in our Can We Trust the 80 Plus Certification? article. Another explanation is the load pattern used by 80 Plus. We emphasize load on the +12 V output, as computers nowadays will pull most of their power from this output, since this is where the CPU and the video cards are connected to.

ST-650P-AF presented a good 84% efficiency when we pulled between 40% and 60% from its labeled capacity (i.e., between 260 W and 390 W), dropping to around 83% when we pulled 80% from its maximum capacity (i.e., 520 W). At light load (20% load, i.e., 130 W) it presented efficiency around 80%, dropping below the 80% mark at full load.

It is important to note that we’ve tested two samples from this power supplies and both achieved identical results.

Voltage regulation was the highlight from ST-650P-AF. All voltages were closer to their nominal values than required, always staying below 3% of their official values (ATX specification allows voltages to be up 5% from their nominal values). This includes the -12 V output, which usually doesn’t like to stay in such tight tolerance.

Noise and ripple levels were below the maximum allowed, as you can see below. All values are peak-to-peak figures and the maximum allowed is 120 mV for the +12 V outputs and 50 mV for the +5 V and +3.3 V outputs.

Figure 14: +12V1 input from load tester at 662.3 W (72.4 mV).

Figure 15: +12V2 input from load tester at 662.3 W (84.4 mV).

Figure 16: +5V rail with power supply delivering 662.3 W (25.4 mV).

Figure 17: +3.3 V rail with power supply delivering 662.3 W (18.4 mV).

Now let’s see if we could pull more than 650 W from this unit.

[nextpage title=”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.

In order to do that we configured the +12V1 input from our load tester (which was connected to the power supply +12V2 rail) with a low current and configured our load tester to pull 33 A from the power supply +12V1 rail. The power supply turned on, meaning that either OCP is disabled or configured at a value above 33 A.

Then starting from test five we increased currents to the maximum we could with the power supply still running inside ATX specs. The problem was that the power supply burned under this condition. Then we requested a second sample from Seventeam and the same thing happened. With our first sample we were pulling 32 A from each +12 V rail and 10 A from +5 V and +3.3 V, for a total of approximately 850 W. With the second sample we tried to pull less (29 A from each +12 V rail) for a total of approximately 785 W.

Of course we’d prefer the power supply shutting down instead of burning, but this should not be seen as a very negative point because in both cases we were overloading the unit a lot.

In both samples the components that burned were the +12 V rectifiers.

[nextpage title=”Main Specifications”]

Seventeam ST-650P-AF power supply specs include:

• ATX12V 2.2
• Nominal labeled power: 650 W.
• Measured maximum power: 785 W at 45.6° C (unit burned under this load).
• Labeled efficiency: 80% minimum (80 Plus Bronze certified)
• Measured efficiency: Between 78.6% and 84.1% at 115 V (nominal, see complete results for actual voltage).
• Active PFC: Yes.
• Modular Cabling System: No.
• Motherboard Power Connectors: One 24-pin connector and two ATX12V connectors that together form an EPS12V connector.
• Video Card Power Connectors: Two six/eight-pin connectors in separated cables.
• SATA Power Connectors: Six in two cables.
• Peripheral Power Connectors: Three in one cable.
• Floppy Disk Drive Power Connectors: One.
• Protections: Over voltage (OVP, not tested), under voltage (UVP, not te
  sted), over current (OCP, tested and not working) and over power (OPP, not working). Short-circuit protection (SCP) present and working.
• Warranty: N/A.
• More Information: https://www.seventeam.com.tw
• Average price in the US*: USD 95.00.

* Researched at Newegg.com on the day we published this review.

[nextpage title=”Conclusions”]

Seventeam ST-650P-AF may be a good buy if you know what you are taking home. It presents a good efficiency (84%) if you pull between 40% and 60% from its labeled capacity (i.e., between 260 W and 390 W), dropping to around 83% if you pull 80% from its maximum capacity (i.e., 520 W). At light load (20% load, i.e., 130 W) it presents efficiency around 80%, dropping below the 80% mark at full load. So you should avoid this power supply if you are going to operate it at light load or at full load. It is important to keep in mind that we test power supplies at high temperatures and that is why efficiency results from our reviews are usually lower than announced by 80 Plus.

Voltage regulation was the highlight from ST-650P-AF. All voltages were closer to their nominal values than required, always staying below 3% of their official values (ATX specification allows voltages to be up 5% from their nominal values). This includes the -12 V output, which usually doesn’t like to stay in such tight tolerance. Noise and ripple levels were below the maximum allowed.

We’d like to remember that internally this power supply is identical to Seventeam ST-650Z-AF and SilverStone ST65EF, so all performance considerations are also valid for these other two products.

Coming with a very attractive USD 95 price tag, ST-650P-AF is a good option for the user that is building a PC that will pull between 260 W and 390 W. If, however, you are looking for “the best” 650 W on the market, then you should take a look at a different product.

The only feedback we need to give to Seventeam is for them to fix their website and product box and replace "Japanese capacitors" by "Japanese capacitor on primary" or similar wording, as "capacitors" lead the consumer to think that all capacitors inside the power supply are Japanese, which is not the case.