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The ZT Series is the latest power supply series from OCZ, with a full modular cabling system – meaning that even the main motherboard cable is detachable – and 80 Plus Bronze certification. Available in 550 W, 650 W, and 750 W versions, let’s see if the 650 W model is a good buy.

ZT Series power supplies are manufactured by Great Wall, while the ZS Series power supplies are manufactured by High Power.

OCZ ZT Series 650 W power supplyFigure 1: OCZ ZT Series 650 W power supply

OCZ ZT Series 650 W power supplyFigure 2: OCZ ZT Series 650 W power supply

The OCZ ZT Series 650 W is 6.9” (175 mm) deep, using a 140 mm ball bearing fan on its bottom (Yate Loon D14BH-12).

This unit has a modular cabling system with nine connectors: one for the main motherboard cable, one for the ATX12V/EPS12V cable (black), two for video cards (gray), and five for SATA and peripheral power connectors (black). This power supply comes with the following cables:

  • Main motherboard cable with a 20/24-pin connector, 21.6” (55 cm) long
  • One cable with two ATX12V connectors that together form an EPS12V connector, 23.6” (60 cm) long
  • Two cables, each with one six/eight-pin connector for video cards, 22” (56 cm) long
  • Three cables, each with three SATA power connectors, 15.7” (40 cm) to the first connector, 5.9” (15 cm) between connectors
  • Two cables, each with two standard peripheral power connectors, 15.7” (40 cm) to the first connector, 5.9” (15 cm) between connectors
  • One adapter to convert any standard peripheral power connector into a floppy disk drive power connector

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

The cable configuration is fair for a 650 W power supply, with two video card power connectors and nine SATA power connectors.

OCZ ZT Series 650 W power supplyFigure 3: Cables

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

[nextpage title=”A Look Inside the OCZ ZT Series 650 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.

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. At first appearance, the ZT Series 650 W looks a lot like the ZS Series 650 W internally. However, after a closer inspection we could see that the printed circuit board is not the same, and the ratings of the main components are different. In fact, the ZS Series 650 W is manufactured by High Power, and the ZT Series 650 W is manufactured by Great Wall, so they can’t be based on the same platform.

OCZ ZT Series 650 W power supplyFigure 4: Top view

OCZ ZT Series 650 W power supplyFigure 5: Front quarter view

OCZ ZT Series 650 W power supplyFigure 6: Rear quarter view

OCZ ZT Series 650 W power supplyFigure 7: The 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. 

In this stage, the OCZ ZT Series 650 W power supply has two Y capacitors and one X capacitor more than the minimum required, but it doesn’t have an MOV, which is the component in charge of removing spikes coming from the power grid.

OCZ ZT Series 650 W power supplyFigure 8: Transient filtering stage (part 1)

OCZ ZT Series 650 W power supplyFigure 9: Transient filtering stage (part 2)

On the next page, we will have a more detailed discussion about the components used in the OCZ ZT Series 650 W.

[nextpage title=”Primary Analysis”]

On this page we will take an in-depth look at the primary stage of the Thortech Thunderbolt 850 W. For a better understanding, please read our “Anatomy of Switching Power Supplies” tutorial.

This power supply uses two T10KB60 rectifying bridges, which are attached to an individual heatsink. Each bridge supports up to 10 A at 100° C, so in theory, you would be able to pull up to 2,300 W from a 115 V power grid. Assuming 80% efficiency, the bridges would allow this unit to deliver up to 1,840 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.

OCZ ZT Series 650 W power supplyFigure 10 : Rectifying bridges

The active PFC circuit uses two FDA24N50 MOSFETs, each one supporting up to 24 A at 25° C or 14 A at 100° C in continuous mode (note the difference temperature makes), or 96 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.

OCZ ZT Series 650 W power supplyFigure 11: The active PFC diode and transistors

The output of the active PFC circuit is filtered by a 560 µF x 420 V electrolytic capacitor, from Teapo, labeled at 85° C.

In the switching section, two FDP20N50 MOSFETs are employed using the traditional two-transistor forward configuration. Each transistor supports up to 20 A at 25° C or 12.9 A at 100° C in continuous mode, or 80 A at 25° C in pulse mode, with a 230 mΩ RDS(on).

OCZ ZT Series 650 W power supplyFigure 12: The switching transistors

The switching transistors are controlled by the famous CM6800 PWM/active PFC combo controller.

OCZ ZT Series 650 W power supplyFigure 13: Active PFC/PWM controller

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

[nextpage title=”Secondary Analysis”]

The OCZ ZT Series 650 W uses a semi-synchronous design on the +12 V output: the direct rectification is performed by two MOSFETs, but the “freewheeling” part of the rectification is done by two Schottky rectifiers. The replacement of diodes with transistors is made in order to increase efficiency, but usually, all the diodes are replaced rather than only half, as in this case.

The +12 V output uses two QM6020AP MOSFETs, each one supporting up to 198 A at 25° C or 125 A at 100° C in continuous mode, or 350 A at 25° C in pulse mode, with a 3.8 mΩ RDS(on), and two PFR60L60CT Schottky rectifiers (60 A, 30 A per internal diode at 100° C, 0.65 V maximum voltage drop).

The +5 V output uses two PFR30L45CT Schottky rectifiers (30 A, 15 A per internal diode at 100° C, 0.52 V maximum voltage drop), which gives us a maximum theoretical current of 43 A or 214 W for this output.

The +3.3 V output uses two PFR20L45CT Schottky rectifiers (20 A, 10 A per internal diode at 120° C, 0.50 V maximum voltage drop), which gives us a maximum theoretical current of 29 A or 94 W for this output.

OCZ ZT Series 650 W power supplyFigure 14: The +12 V transistors, +12 V rectifiers, +5 V rectifiers, and +3.3 V rectifiers

This power supply uses an ST9S424 monitoring integrated circuit. Unfortunately, the datasheet for this component is not available at the manufacturer’s website, so we can’t comment on the protections that this power supply actually supports.

OCZ ZT Series 650 W power supplyFigure 15: Monitoring circuit

The electrolytic capacitors that filter the outputs are Japanese, from Chemi-Con, and are labeled at 105° C, as usual.

[nextpage title=”Power Distribution”]

In Figure 16, you can see the power supply label containing all the power specs.

OCZ ZT Series 650 W power supplyFigure 16: Power supply label

This power supply has a single +12 V rail, so there is not much to talk about here.

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

[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 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, the +12VA and +12VB 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) 10 A (120 W) 15 A (180 W) 20 A (240 W) 24 A (288 W)
+12VB 5 A (60 W) 10 A (120 W) 15 A (180 W) 20 A (240 W) 24 A (288 W)
+5 V 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 (13.2 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 141.2 W 270.2 W 408.5 W 545.9 W 652.8 W
% Max Load 21.7% 41.6% 62.8% 84.0% 100.4%
Room Temp. 46.6° C 46.3° C 48.4° C 44.8° C 45.8° C
PSU Temp. 49.0° C 48.9° C 49.6° C 46.9° C 47.8° C
Voltage Regulation Pass Pass Pass Pass Pass
Ripple and Noise Pass Pass Pass Pass Pass
AC Power 165.9 W 311.4 W 476.0 W 650.0 W 795.0 W
Efficiency 85.1% 86.8% 85.8% 84.0% 82.1%
AC Voltage 115.5 V 113.6 V 111.9 V 111.5 V 109.6 V
Power Factor 0.983 0.991 0.993 0.995 0.997
Final Result Pass Pass Pass Pass Pass

The OCZ ZT Series 650 W passed our tests with flying colors.

Efficiency was between 82.1% and 86.8% during our tests, perfectly matching the 80 Plus Bronze certification. As you know, there are several power supplies with the 80 Plus Bronze certification that can’t deliver 82% efficiency at full load under high temperatures.

Voltages were closer to their nominal values (3% regulation) during all tests, which is terrific. The ATX12V specification states that 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.

[nextpage title=”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 OCZ ZT Series 650 W provided extremely 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 11.4 mV 14.2 mV 19.4 mV 23.6 mV 30.8 mV
+12VB 13.2 mV 16.2 mV 20.4 mV 24.8 mV 31.2 mV
+5 V 16.2 mV 12.0 mV 11.4 mV 13.4 mV 13.8 mV
+3.3 V 6.6 mV 7.2 mV 7.4 mV 8.8 mV 8.2 mV
+5VSB 8.2 mV 8.6 mV 8.8 mV 8.6 mV 8.4 mV
-12 V 23.0 mV 25.6 mV 32.4 mV 41.6 mV 50.6 mV

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

OCZ ZT Series 650 W power supplyFigure 17: +12VA input from load tester during test five at 652.8 W (30.8 mV)

OCZ ZT Series 650 W power supplyFigure 18: +12VB input from load tester during test five at 652.8 W (31.2 mV)

OCZ ZT Series 650 W power supplyFigure 19: +5V rail during test five at 652.8 W (13.8 mV)

OCZ ZT Series 650 W power supplyFigure 20: +3.3 V rail during test five at 652.8 W (8.2 mV)

Let’s see if we can pull more than 650 W from this unit.

[nextpage title=”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, voltages were still within 3% of their nominal values, while ripple and noise levels were still very low.

Input Overload Test
+12VA 28 A (336 W)
+12VB 28 A (336 W)
+5 V 8 A (40 W)
+3.3 V 8 A (26.4 W)
+5VSB 3 A (15 W)
-12 V 0.5 A (6 W)
Total 750.8 W
% Max Load 115.5%
Room Temp. 43.8° C
PSU Temp. 48.2° C
AC Power 933 W
Efficiency 80.5%
AC Voltage 107.9 V
Power Factor 0.998
[nextpage title=”Main Specifications”]

The main specifications for the OCZ ZT Series 650 W power supply include:

  • Standards: ATX12V 2.2
  • Nominal labeled power: 650 W at 45° C
  • Measured maximum power: 750.8 W at 43.8° C
  • Labeled efficiency: Up to 85%, 80 Plus Bronze certification
  • Measured efficiency: Between 82.1% and 86.8%, at 115 V (nominal, see complete results for actual voltage)
  • Active PFC: Yes
  • Modular Cabling System: Yes, full
  • Motherboard Power Connectors: One 20/24-pin connector and two ATX12V connectors that together form an EPS12V connector
  • Video Card Power Connectors: Two six/eight-pin connectors on separate cables
  • SATA Power Connectors: Nine on three cables
  • Peripheral Power Connectors: Six on two cables
  • Floppy Disk Drive Power Connectors: One, converted from a standard peripheral power connector
  • Protections (as listed by the manufacturer): Over voltage (OVP), over current (OCP), over power (OPP), and short-circuit (SCP) protections
  • Are the above protections really available? Couldn’t confirm.
  • Warranty: Five years
  • Real Manufacturer: Great Wall
  • More Information: https://www.ocztechnology.com
  • Average Price in the US*: USD 100.00

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

[nextpage title=”Conclusions”]

The OCZ ZT Series 650 W proved to be a flawless power supply, with high efficiency between 82.1% and 86.8%, voltages closer to their nominal values all the time (3% regulation), very low noise and ripple levels, and a fully modular cabling system. All of that sells at a terrific price of USD 100, making this product a no-brainer if you are looking for the “perfect” power supply with a full modular cabling system. It costs only USD 10 more than the OCZ ZS Series 650 W, which has similar performance but no modular cabling system.

By the way, in this review we could clearly see that the ZT Series 650 W is not a ZS Series 650 W with the modular cabling system added; they use different components and design.

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