OCZ ZT Series 750W PSU

PSU might be one of the neglected upgrades for most PC users, but power users should realize that when you need stable system, longer component life and more peripherals attached like dual 3D Cards then a good PSU is indispensable requirement.

Luckily OCZ has a great line-up of power supplies for consumers including ZS for budget PCs, ZX for high-end users while ZT falls right in between by providing a good balance between features, power and affordability; ZT 750W is a shining example of this how they made available a fully modular PSU at low cost to consumers.

PACKAGING

OCZ ZT Series 750W PSU

OCZ ZT Series 750W PSU

The PSU comes in good quality cloth cover to protect from scratches and comes with following cables :

  1. ATX 20+4 pin : 1 cable
  2. CPU 4+4 pin : 2 cables
  3. PCI-Express 6+2 pin : 4 cables
  4. Peripheral/IDE 4 pin : 2 cables x 3 connectors
  5. SATA : 3 cables x 3 connectors
  6. Floppy : 1 cable

VOLTAGE REGULATION

The on-box specifications for this PSU are shown below:

PSU specifications

PSU specifications

And we tested every line of PSU on varying loads to check voltage regulation first. Normally all PC components are designed to work well within a plus minus 5% voltage variation (i.e. from 95% to 105%). So, a good PSU should be able to maintain as low as possible variation. The test results for OCZ ZT 750W were as follow:

test OCZ ZT 750W

Test results for OCZ ZT 750W

The maximum variation ZT 750W showed was of 3% which is very reasonable; moreover that variation is only for 3.3V line which isn’t that critical. Our main concern was the 12V line and that one only showed a variation of 2% which is what we would be expect from good quality PSUs in competition with ZT 750W.

Load Unit 12V 5V 3.3V 5VSB
20% A 10.554 1.992 1.943 1.001
V 12.20 5.06 3.35 5.02
40% A 21.55 4.03 3.93 1.21
V 12.14 5.01 3.31 5.00
50% A 26.96 5.05 4.92 1.62
V 12.11 4.99 3.30 4.98
60% A 32.41 6.10 5.95 2.03
V 12.08 4.97 3.28 4.96
80% A 43.56 8.19 8.02 2.45
V 12.01 4.93 3.24 4.93
100% A 55.05 9.28 9.10 4.15
V 11.94 4.89 3.21 4.84

CROSS-LOADS

PSUs use common regulator for different rails to keep cost low, but that also means that the ideal regulation of each rail independent of other’s load is not maintainable. So, e.g. when you run a 3D game load will increase on your 12V rail and PSU will give more power to it but since the regulator is same so voltage on non-primary rails will also vary.

As per ATX specifications, the variation should remain within 5% for machine to remain stable. So, to check this performance other than independent rails regulation, we also did two test for crossloads. One crossload maxes out the non-primary rails while the other load maxes out the +12V.

Cross-Loads Regulation

Cross-Loads Regulation

Voltage 12V 5V 3.3V 5VSB
Crossload 1 12.18 4.91 3.34 5.01
Crossload 2 12.00 4.98 3.34 4.99

The results showed very nice regulation under cross-loads with maximum variation going up to 1.8% which is well below the 5% allowed value, so the PSU will provide very stable output under real world applications.

EFFICIENCY

The PSU feature a 80 plus bronze efficiency which does mean that it should be able to perform above 82% under full load. Efficiency is a quick measure of how much PSU will be producing output power based on input to it. Cheap PSUs may go as low as 60%, meaning that if it draws 750W from power socket, it will only be delivering a power of 450W to PSU.

Whereas a 80 plus Bronze will deliver 615W output from 750W input. Here is a chart to show what different 80 plus certifications exist for consumers to easily recognize the efficiency of PSU:

Efficiency

Efficiency

In detail 80 plus bronze would require:

  • 82% efficiency at 100% load
  • 85% efficiency at 50% load
  • 82% efficiency at 20% load

Our test results showed the following results:

Test results

Test results

Load Output (W) Input (W) PSU Efficiency
20% 150 181.0 82.87%
50% 375 442.0 84.84%
100% 750 925.0 81.08%

OCZ has managed to very closely follow recommended criteria, at low load we even managed to get better efficiency while at full load its marginally less but it can be considered as test or reading error.

RIPPLE TEST

We tested the ripples in voltage supplied over time and found that OCZ ZT 750W supplies a very stable volt over time.

According to ATX specification the limits are 120 mV for 12V rail and the PSU was able to manage the variation from +20mV to -15mV which is pretty nice.

OCZ ZT 750W Ripple Test

OCZ ZT 750W Ripple Test

For 5V, 3.3V and 5VSB ATX specifications limit acceptable variation to be 50mV, the worst case we found was for 5V rail amongst these and even that remained from +10mV to -15mV confirming the stable voltage this PSU is able to deliver.

OCZ ZT 750W Cross-Load

OCZ ZT 750W Cross-Load

CONCLUSION

Even though its reasonable value (~ $110), this PSU passed every test we threw at it with flying colors. The whole time the temperature remained below 42 degree C. The maximum temp for which this PSU is designed is 45 which is already below the 50 C maximum set by ATX specification. We do have complaint about the sound of the fan as it seemed pretty loud at times. We even tried different orientations of the PSU but it is a but loud as compared to other PSUs we have used.

But if a little sound is no issue for you then performance wise this PSU wins our heart. Its as efficient as expected. The primary +12V rail voltage regulation is really controlled and ripples are suppressed. And in the end the modular design with plethora of options to build your PC at this price makes this an absolutely fantastic PSU amongst its peers, compelling us to give it our “Recommended Value” award.

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