Corsair TX850 V2 Power Supply Review

[nextpage title=”Introduction”]

Let’s take a look at the revamped Corsair TX850 power supply, dubbed TX850 V2, now featuring a DC-DC design and 80 Plus Bronze certification. It is important to understand that while the old TX850 was manufactured by CWT, being a relabeled 850VH unit from this manufacturer, the new Corsair TX850 V2 is manufactured by Seasonic, being internally identical to the XFX PRO 850 W unit.

The only differences between the Corsair TX850 V2 and the XFX PRO 850 W are the fan (140 mm on the Corsair model and 135 mm on the XFX model), the configuration of the video card connectors (four six/eight-pin on the Corsair model and two six-pin and two six/eight-pin on the XFX model), and the configuration of the peripheral power cables (two cables with four standard peripheral power connectors and one floppy disk drive power connector each on the Corsair model and one cable with four standard peripheral power connectors and one cable with three peripheral power connectors and one floppy disk drive power connector on the XFX model).

Figure 1: Corsair TX850 V2 power supply

Figure 2: Corsair TX850 V2 power supply

The TX850 V2 is 6.3” (160 mm) deep, with a 140 mm dual ball bearing fan (Yate Loon D14BH-12, 2,800 rpm, 140 cfm, 48.5 dB) on its bottom part.

The new Corsair TX850 V2 doesn’t have a modular cabling system. All cables are protected with nylon sleeves. The power supply comes with the following cables:

• Main motherboard cable with a 20/24-pin connector, 23.2” (59 cm) long
• One cable with two ATX12V connectors that together form an EPS12V connector, 23.6” (60 cm) long
• Four cables, each with one six/eight-pin connector for video cards, 23.6” (60 cm) long
• Two cables, each with four SATA power connectors, 16.1” (41 cm) to the first connector, 5.9” (15 cm) between connectors
• Two cables, each with four standard peripheral power connectors and one floppy disk drive power connector, 15.7” (40 cm) to the first connector, 5.5” (14 cm) between connectors

This is the exact same configuration used on the Corsair TX750 V2.

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

The cable configuration is adequate for an 850 W unit, but we’d be happier if this unit carried six cables for video cards, allowing you to install up to three high-end video cards without the need of adapters. Of course, having so many cables would be a hassle on a power supply without a modular cabling system.

Figure 3: Cables

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

[nextpage title=”A Look Inside the Corsair TX850 V2″]

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. As already explained, the Corsair TX850 V2 is internally identical to the XFX PRO 850 W.

Figure 4: Top view

Figure 5: Front quarter view

Figure 6: Rear quarter view

Figure 7: Printed circuit board

[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 of the Corsair TX850 V2 is impeccable, coming with all required components plus one extra X capacitor, one extra ferrite coil, and four extra Y capacitors.

Figure 8: Transient filtering stage (part 1)

Figure 9: Transient filtering stage (part 2)

Now let’s have a more detailed discussion of the components used in the Corsair TX850 V2.

[nextpage title=”Primary Analysis”]

On this page we will take an in-depth look at the primary stage of the Corsair TX850 V2. For a better understanding, please read our Anatomy of Switching Power Supplies tutorial.

This power supply uses two GBU806 rectifying bridges connected in parallel, both attached to an individual heatsink. Each bridge supports up to 8 A at 100° C, so in theory, you would be able to pull up to 1,840 W from a 115 V power grid. Assuming 80% efficiency, the bridges would allow this unit to deliver up to 1,472 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. These are the same bridges used in the 750 W version.

Figure 10: Rectifying bridges

The active PFC circuit uses two SPP24N60C3 MOSFETs, which are capable of delivering up to 24.3 A at 25° C or up to 15.4 A at 100° C in continuous mode (note the difference temperature makes), or up to 72.9 A in pulse mode at 25° C, each. These transistors present a 160 mΩ resistance when turned on, a characteristic called RDS(on). The lower this number the better, meaning that the transistors will waste less power and the power supply will achieve a higher efficiency. It is interesting to note how, in order to improve thermal dissipation, the manufacturer added a metallic plate between these transistors and the aluminum heatsink (see Figure 11). These are the same transistors used in the 750 W model.

Figure 11: Active PFC transistors

This power supply uses two 330 µF x 400 V electrolytic capacitors to filter the output from the active PFC circuit; this is the equivalent of one 660 µF x 400 V capacitor. The Corsair TX750 V2 uses one 220 µF x 400 V and one 330 µF x 400 V capacitors connected in parallel. The capacitors are Japanese, from Rubycon, and labeled at 105° C.

In the switching section, another two SPP24N60C3 MOSFET transistors are used, installed in the two-transistor forward configuration. The specifications for these transistors were already published above. The 750 W model uses transistors with lower current limits (20.7 A at 25° C or 13.1 A at 100° C).

Figure 12: One of the switching transistors

The primary is controlled by a CM6802 active PFC/PWM combo controller.

Figure 13: Active 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 a DC-DC project in its secondary, meaning that this unit is basically a +12 V power supply, with the +5 V and +3.3 V outputs produced by two smaller switching power supplies connected to the +12 V rail. This design is used in order to increase efficiency.

The +12 V output makes use of six SBR30A50CT Schottky rectifiers (30 A, 15 A per internal diode at 110° C, 0.55 V maximum voltage drop). From the available 12 diodes (two per rectifier pack), eight are used in the direct rectification, and four are used in the “freewheeling” part of the rectification. The 750 W model has five Schottky rectifiers here.

Figure 14: The +12 V rectifiers

As explained, the +5 V and +3.3 V outputs are generated using two DC-DC converters (i.e., two switching power supplies). Usually, power supplies using this design have these two converters installed on separate daughterboards, but in the Corsair TX850 V2 they are available on the same board, shown in Figures 15 and 16. The two converters are managed by the same PWM chip (APW7159) and use seven APM2556N MOSFET transistors, each one being able to handle up to 160 A at 25° C or 90 A at 100° C with an RDS(on) of only 4.5 mΩ. This board is identical to the one used in the 750 W version.

Figure 15: The +5 V and +3.3 V DC-DC converters

Figure 16: The +5 V and +3.3 V DC-DC converters

The secondary is monitored by a PS223 integrated circuit, which supports over voltage protection (OVP), under voltage protection (UVP), over current protection (OCP), and over temperature protection (OTP). This integrated circuit has four OCP channels (+3.3 V, +5 V and two +12 V), but the manufacturer decided to use only one of the +12 V channels, making this a single-rail power supply.

Figure 17: Monitoring circuit

All electrolytic capacitors used in the secondary are also Japanese, from Chemi-Con, and labeled at 105° C.

[nextpage title=”Power Distribution”]

In Figure 18, you can see the power supply label containing all the power specs.

Figure 18: Power supply label

Since this unit has a single +12 V rail, there is not much to talk about here.

Let’s now see if this power supply can really deliver 850 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 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 m
ay 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 our tests, the +12VA and +12VB input were connected to the power supply single +12 V rail (the EPS12V connector was installed on the +12VB input of our load tester).

Input	Test 1	Test 2	Test 3	Test 4	Test 5
+12VA	6 A (72 W)	13 A (156 W)	20 A (240 W)	25 A (300 W)	31 A (372 W)
+12VB	6 A (72 W)	13 A (156 W)	17 A (204 W)	25 A (300 W)	31 A (372 W)
+5 V	2 A (10 W)	4 A (20 W)	6 A (30 W)	8 A (40 W)	10 A (50 W)
+3.3 V	2 A (6.6 W)	4 A (13.2 W)	6 A (30 W)	8 A (26.4 W)	10 A (33 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	172.8 W	348.3 W	510.5 W	683.9 W	848.4 W
% Max Load	20.3%	41.0%	60.1%	80.5%	99.8%
Room Temp.	44.8° C	46.2° C	45.4° C	45.6° C	46.4° C
PSU Temp.	46.7° C	48.2° C	49.6° C	50.8° C	52.5° C
Voltage Regulation	Pass	Pass	Pass	Pass	Pass
Ripple and Noise	Pass	Pass	Pass	Pass	Pass
AC Power	204.1 W	405.9 W	599.2 W	817.0 W	1037.0 W
Efficiency	84.7%	85.8%	85.2%	83.7%	81.8%
AC Voltage	116.5 V	113.2 V	111.0 V	108.9 V	106.1 V
Power Factor	0.985	0.992	0.996	0.998	0.998
Final Result	Pass	Pass	Pass	Pass	Pass

The Corsair TX850 V2 can really deliver its labeled wattage at high temperatures.

Efficiency was very good, above 83% when we pulled between 20% and 80% of the labeled wattage (i.e., between 170 W and 680 W). At 850 W, efficiency dropped to 81.8%, just a hair below the minimum required by the 80 Plus Bronze certification (82%).

Voltage regulation was superb, with all voltages within 3% of their nominal values, including the -12 V output. The ATX12V specification allows voltages to be up to 5% from their nominal values (10% for the -12 V output). Therefore, this power supply presents voltages closer to their nominal values than necessary all the time.

Noise and ripple levels were always extremely low. Below you can see the results for the power supply outputs during test number five. The maximum allowed is 120 mV for the +12 V and -12 V outputs, and 50 mV for the +5 V, +3.3 V, and +5VSB outputs. All values are peak-to-peak figures.

Figure 19: +12VA input from load tester during test five at 848.4 W (19.8 mV)

Figure 20: +12VB input from load tester during test five at 848.4 W (25.6 mV)

Figure 21: +5V rail during test five at 848.4 W (11.4 mV)

Figure 22: +3.3 V rail during test five at 848.4 W (11.4 mV)

Let’s see if we can pull more than 850 W from this unit.

[nextpage title=”Overload Tests”]

Unfortunately, the first sample we receieved burned when we were doing our overload tests (it burned when delivering around 1,000 W). We asked a second sample to the manufacturer, and this sample survived our overload tests. See the results below. We couldn’t pull more than that because the power supply shut down, showing that its protections were working just fine.

Input	Overload Test
+12VA	32.5 A (390 W)
+12VB	33 A (396 W)
+5 V	22 A (110 W)
+3.3 V	22 A (72.6 W)
+5VSB	3 A (15 W)
-12 V	0.5 A (6 W)
Total	978.7 W
% Max Load	115.1%
Room Temp.	47.8° C
PSU Temp.	50.1° C
AC Power	1,263 W
Efficiency	77.5%
AC Voltage	102.9 V
Power Factor	0.997

[nextpage title=”Main Specifications”]

The main specifications for the Corsair TX850 V2 include:

• Standards: ATX12V 2.31 and EPS12V 2.91
• Nominal labeled power: 850 W
• Measured maximum power: NA (see text)
• Labeled efficiency: Up to 85%, 80 Plus Bronze certification
• Measured efficiency: Between 81.8% and 85.8%, at 115 V (nominal, see complete results for actual voltage)
• Active PFC: Yes
• Modular Cabling System: No
• Motherboard Power Connectors: One 20/24-pin connector and two ATX12V connectors that together form an EPS12V connector
• Video Card Power Connectors: Four six/eight-pin connectors on separate cables
• SATA Power Connectors: Eight on two cables
• Peripheral Power Connectors: Eight on two cables
• Floppy Disk Drive Power Connectors: Two on two cables
• Protections (as listed by the manufacturer): NA
• Are the above protections really available? Although not listed by the manufacturer, over voltage (OVP), under voltage (UVP), over current (OCP), over temperature (OTP), over power (OPP), and short-circuit (SCP) protections are available.
• Warranty: Five years
• Real Manufacturer: Seasonic
• More Information: https://www.corsair.com
• Average Price in the US*: USD 135.00

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

[nextpage title=”Conclusions”]

The Corsair TX850 V2 can really deliver its labeled wattage at high temperatures, provides decent efficiency between 82% and 86%, superb voltage regulation, and ultra low noise and ripple levels. In summary, it is a good power supply for the user who is concerned about quality and doesn’t want to spend a lot of money on an 850 W product.

In this review, we discovered that the Corsair TX850 V2 is internally identical to the XFX PRO 850 W, and the only differences between the 850 W and the 750 W models are the use of more powerful switching transistors and one additional Schottky rectifier in the 850 W model.

 Although the TX850 V2 is nicely priced (USD 135 or USD 125 after mail-in rebate), the XFX PRO 850 W costs less (USD 120 or USD 110 after mail-in rebate). Since both power supplies are the same, right now it makes more sense to buy the model from XFX. Interestingly enough, the opposite occurs with the 750 W model; the TX750 V2 is a little cheaper than the XFX PRO 750 W. Who said, “Competition isn’t healthy?”