Corsair TX750M Power Supply Review
By Gabriel Torres on September 7, 2011


Introduction

Hardware Secrets Bronze Award

Corsair is releasing the third version of their popular TX power supply series, dubbed “M,” for “Modular.” However, it is really important to understand that this new version isn’t simply a TX or TX V2 power supply with a modular cabling system added; the internal design is completely different. The TX M series has 550 W, 650 W, 750 W, and 850 W models, all with 80 Plus Bronze certification. (The TX V2 series doesn’t have a 550 W version, and Corsair still offers a 950 W model under the first TX series.) Let’s take a look at the 750 W version of the TX M series.

The manufacturer behind the TX M series is CWT, the same manufacturer that was in charge of the first version of the TX series. The TX V2 series, however, is manufactured by a different company (Seasonic). Therefore, the TX M series power supplies can’t be TX V2 units with a modular cabling system added. We’ve already reviewed the first version of the TX750 and the TX750 V2, in case you want to compare the new TX750M to the previous two models. 

Corsair TX750M power supply
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Figure 1: Corsair TX750M power supply

Corsair TX750M power supply
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Figure 2: Corsair TX750M power supply

The Corsair TX750M is 6.3” (160 mm) deep, using a 140 mm ball bearing fan on its bottom (Yate Loon D14BH-12).

As explained, this unit has a modular cabling system, with six cables permanently attached to the power supply, using nylon sleeves. The modular cabling system has four connectors, two black for SATA/peripheral power connectors and two blue for video card or EPS12V power connectors. This power supply comes with the following cables:

All wires are 18 AWG, which is the minimum recommended gauge.

The cable configuration is good for a 750 W product, with eight SATA power connectors and four video card power connectors.

Corsair TX750M power supply
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Figure 3: Cables

Let’s now take an in-depth look inside this power supply.

A Look Inside the Corsair TX750M

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.

On this page we will have an overall look, and then in the following pages we will discuss in detail the quality and ratings of the components used.

Corsair TX750M power supply
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Figure 4: Top view

Corsair TX750M power supply
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Figure 5: Front quarter view

Corsair TX750M power supply
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Figure 6: Rear quarter view

Corsair TX750M power supply
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Figure 7: The printed circuit board

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. 

In this stage, this power supply is flawless, with one X capacitor and two Y capacitors more than the minimum required.

Corsair TX750M power supply
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Figure 8: Transient filtering stage (part 1)

Corsair TX750M power supply
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Figure 9: Transient filtering stage (part 2)

On the next page, we will have a more detailed discussion about the components used in the Corsair TX750M.

Primary Analysis

On this page we will take an in-depth look at the primary stage of the Corsair TX750M. For a better understanding, please read our Anatomy of Switching Power Supplies tutorial.

This power supply uses two GBU606 rectifying bridges, attached to an individual heatsink. These bridges support up to 6 A at 100° C each, so in theory, you would be able to pull up to 1,380 W from a 115 V power grid. Assuming 80% efficiency, the bridges would allow this unit to deliver up to 1,104 W without burning themselves out. Of course, we are only talking about these particular components. The real limit will depend on all the components combined in this power supply.

Corsair TX750M power supply
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Figure 10: Rectifying bridges

The active PFC circuit uses two SPW20N60C3 MOSFETs, each supporting up to 20.7 A at 25° C or 13.1 A at 100° C in continuous mode (note the difference temperature makes), or 62.1 A at 25° C in pulse mode. These transistors present a 190 mΩ resistance when turned on, a characteristic called RDS(on). The lower the number the better, meaning that the transistor will waste less power, and the power supply will have a higher efficiency.

Corsair TX750M power supply
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Figure 11: Active PFC transistors

The output of the active PFC circuit is filtered by a Japanese capacitor from Panasonic, labeled at 105° C.

In the switching section, two SiHG20N50C MOSFETs are used in the traditional two-transistor forward configuration. Each transistor supports up to 20 A at 25° C or 11 A at 100° C in continuous mode or up to 80 A at 25° C in pulse mode, with an RDS(on) of 270 mΩ.

Corsair TX750M power supply
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Figure 12: Switching transistors

The primary is controlled by the popular CM6800 active PFC/PWM combo controller.

Corsair TX750M power supply
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Figure 13: Active PFC/PWM combo controller

Let’s now take a look at the secondary of this power supply.

Secondary Analysis

The Corsair TX750M uses a DC-DC design in its secondary, meaning that this power supply is basically a +12 V unit, with the +5 V and +3.3 V outputs being generated by two smaller switch-mode power supplies connected to the main +12 V output. This design is proving to be the best solution to achieve high efficiency.

The +12 V output uses five SBR40U60CT Schottky rectifiers (40 A, 20 A per diode at 150° C, 0.60 V maximum voltage drop). They are configured as shown in Figure 15.

Corsair TX750M power supply
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Figure 14: The +12 V rectifiers

Corsair TX750M power supply
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Figure 15: How the rectifiers are connected

The +5 V and +3.3 V power supplies are located on the same printed circuit board as the modular cabling system, as you can see in Figures 16 and 17. They use one APW7159 PWM controller, and each output is driven by four AP72T03GH MOSFETs (up to 62 A at 25° C or 44 A at 100° C in continuous mode, or up to 190 A at 25° C in pulse mode, 9 mΩ resistance).

Corsair TX750M power supply
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Figure 16: The DC-DC converters

Corsair TX750M power supply
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Figure 17: The DC-DC converters

This power supply uses a PS113 monitoring integrated circuit, which is a very simple chip that supports only over voltage (OVP) and short-circuit (SCP) protections. The protection circuitry also uses an LM393 voltage comparator, probably to add the missing protections.

Corsair TX750M power supply
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Figure 18: Monitoring circuit

The electrolytic capacitors that filter the +5 V and +3.3 V rails are solid, while the capacitors that filter the +12 V rails are Japanese, from Chemi-Con.

Power Distribution

In Figure 19, you can see the power supply label containing all the power specs.

Corsair TX750M power supply
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Figure 19: Power supply label

This power supply uses a single-rail design, so there is not much to talk about here.

How much power can this unit really deliver? Let’s find out.

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 the behavior of the reviewed unit 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 powers listed for each test, you may find a different value than what is posted under “Total” below. Since each output can have a slight variation (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. In the “Total” row, we are using the real amount of power being delivered, as measured by our load tester.

The +12VA and +12VB inputs listed below are the two +12 V independent inputs from our load tester. During this test, both inputs were connected to the power supply’s single +12 V rail.

Input

Test 1

Test 2

Test 3

Test 4

Test 5

+12VA

5 A (60 W)

11 A (132 W)

16 A (192 W)

22 A (264 W)

27 A (324 W)

+12VB

5 A (60 W)

10 A (120 W)

16 A (192 W)

21 A (252 W)

27 A (324 W)

+5 V

2 A (10 W)

4 A (20 W)

6 A (30 W)

8 A (40 W)

11 A (50 W)

+3.3 V

2 A (6.6 W)

4 A (13.2 W)

6 A (19.8 W)

8 A (26.4 W)

11 A (50 W)

+5VSB

1 A (5 W)

1.5 A (7.5 W)

2 A (10 W)

2.5 A (12.5 W)

3 A (15 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

148.2 W

298.9 W

448.0 W

596.1 W

749.3 W

% Max Load

19.8%

39.9%

59.7%

79.5%

99.9%

Room Temp.

45.3° C

45.2° C

45.9° C

48.1° C

49.2° C

PSU Temp.

51.0° C

51.0° C

51.4° C

52.6° C

54.4° C

Voltage Regulation

Pass

Pass

Pass

Pass

Pass

Ripple and Noise

Pass

Pass

Pass

Pass

Pass

AC Power

175.5 W

346.6 W

525.9 W

717.0 W

940.0 W

Efficiency

84.4%

86.2%

85.2%

83.1%

79.7%

AC Voltage

115.7 V

114.0 V

111.9 V

109.4 V

108.1 V

Power Factor

0.982

0.994

0.997

0.998

0.998

Final Result

Pass

Pass

Pass

Pass

Pass

The Corsair TX750M can really deliver its labeled wattage at high temperatures.

Efficiency was between 83.1% and 86.2% when we pulled between 20% and 80% of the unit’s labeled power (i.e., between 150 W and 600 W). At full load (750 W), efficiency dropped to 79.7%, way below the 82% required by the 80 Plus Bronze certification. However, the 80 Plus certification tests are conducted at a room temperature of only 23° C, and efficiency drops as temperature increases. In other words, this unit wouldn’t get the 80 Plus Bronze certification if we were the ones setting their methodology.

Voltages were closer to their nominal values (3% regulation) during all tests, which is terrific. The ATX12V specification says positive voltages must be within 5% of their nominal values, and negative voltages must be within 10% of their nominal values.

Let’s discuss the ripple and noise levels on the next page.

Ripple and Noise Tests

Voltages at the power supply outputs must be as “clean” as possible, with no noise or oscillation (also known as “ripple”). The maximum ripple and noise levels allowed are 120 mV for +12 V and -12 V outputs, and 50 mV for +5 V, +3.3 V and +5VSB outputs. All values are peak-to-peak figures. We consider a power supply as being top-notch if it can produce half or less of the maximum allowed ripple and noise levels.

The Corsair TX750M provided really low ripple and noise levels, as you can see in the table below.

Input

Test 1

Test 2

Test 3

Test 4

Test 5

+12VA

10.4 mV

14.4 mV

21.4 mV

27.6 mV

37.2 mV

+12VB

12.0 mV

17.2 mV

25.8 mV

34.2 mV

45.2 mV

+5 V

7.2 mV

7.6 mV

7.2 mV

8.2 mV

10.4 mV

+3.3 V

7.8 mV

8.8 mV

8.8 mV

10.6 mV

13.4 mV

+5VSB

10.2 mV

10.8 mV

12.6 mV

14.2 mV

17.6 mV

-12 V

15.8 mV

23.8 mV

36.8 mV

51.4 mV

67.2 mV

Below you can see the waveforms of the outputs during test five.

Corsair TX750M power supply
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Figure 20: +12VA input from load tester during test five at 749.3 W (37.2 mV)

Corsair TX750M power supply
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Figure 21: +12VB input from load tester during test five at 749.3 W (45.2 mV)

Corsair TX750M power supply
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Figure 22: +5V rail during test five at 749.3 W (10.4 mV)

Corsair TX750M power supply
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Figure 23: +3.3 V rail during test five at 749.3 W (13.4 mV)

Let’s see if we can pull more than 750 W from this unit.

Overload Tests

Below you can see the maximum we could pull from this power supply. We couldn’t pull more than that because the power supply shut down, showing that its protections were working well. During this test, the +3.3 V output exited the tighter 3% regulation, at +3.17 V, still inside the proper range. Ripple and noise levels were still low, but on the -12 V, which increased to 92.2 mV.

Input

Overload Test

+12VA

30 A (360 W)

+12VB

30 A (360 W)

+5 V

20 A (100 W)

+3.3 V

20 A (66 W)

+5VSB

3 A (15 W)

-12 V

0.5 A (6 W)

Total

890.5 W

% Max Load

118.7%

Room Temp.

44.4° C

PSU Temp.

49.8° C

AC Power

1,158 W

Efficiency

76.9%

AC Voltage

103.3 V

Power Factor

0.998

Main Specifications

The main specifications for the Corsair TX750M power supply include:

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

Conclusions

The Corsair TX750M can really deliver its labeled power at high temperatures, its voltages are closer to their nominal values than required (3% voltage regulation), and it has very low ripple and noise levels.

Efficiency is very good if you pull up to 80% of the unit’s labeled wattage (i.e., up to 600 W), between 83.1% and 86.2%. When delivering 750 W at high temperatures, however, efficiency drops a little bit below the 80% mark.

The TX750M is a good power supply for the average user that won’t be pulling close to 750 W. But if you are the kind of user who demands only “the best in class,” you will be better off buying a different power supply.

At USD 130, the price for the Corsair TX750M is right. Our most common recommendation for a 750 W power supply with modular cabling system for the average user, the XFX 750 W Black Edition, is currently discontinued, but some places still carry it for around USD 150. A better option for this segment, however, is the Enermax NAXN 82+ 750 W, which provides similar features with higher efficiency and lower price point (USD 120).

Originally at http://www.hardwaresecrets.com/article/Corsair-TX750M-Power-Supply-Review/1374


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