Seasonic FOCUS Plus 750 Gold PSU Review

Load Regulation, Hold-Up Time & Inrush Current

To learn more about our PSU tests and methodology, please check out How We Test Power Supply Units. 

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Primary Rails And 5VSB Load Regulation

Load Regulation testing is detailed here.

Hold-Up Time

Our hold-up time tests are described in detail here.

The hold-up time we measure is much longer than the ATX spec's required 17ms. Moreover, Seasonic's power-good signal is accurate; it drops before the rails go out of spec.

Inrush Current

For details on our inrush current testing, please click here.

The inrush current is suppressed efficiently by an NTC thermistor.

Load Regulation And Efficiency Measurements

The first set of tests reveals the stability of the voltage rails and the SSR-750FX's efficiency. The applied load equals (approximately) 10 to 110 percent of the PSU's maximum load in increments of 10 percentage points.

We conducted two additional tests. During the first, we stressed the two minor rails (5V and 3.3V) with a high load, while the load at +12V was only 0.1A. This test reveals whether a PSU is compatible with Intel's C6/C7 sleep states or not. In the second test, we determined the maximum load the +12V rail could handle with minimal load on the minor rails.

Test #12V5V3.3V5VSBDC/AC (Watts)EfficiencyFan Speed
PSU Noise
Temps (In/Out)PF/AC Volts
14.380A1.996A1.994A0.981A74.72185.411%0 RPM<6.0 dB(A)
42.05°C0.955
12.131V5.012V3.303V5.095V87.48438.38°C115.20V
29.797A2.992A2.999A1.180A149.73289.414%0 RPM<6.0 dB(A)42.62°C0.983
12.132V5.008V3.299V5.083V167.45938.80°C115.20V
315.560A3.498A3.517A1.379A224.86090.296%700 RPM14.6 dB(A)38.85°C0.989
12.132V5.004V3.295V5.071V249.02652.18°C115.19V
421.307A4.004A4.008A1.580A299.70590.300%550 RPM10.4 dB(A)39.00°C0.991
12.132V5.000V3.292V5.059V331.90053.36°C115.19V
526.716A5.002A5.014A1.780A374.62889.703%560 RPM10.5 dB(A)40.37°C0.990
12.134V4.996V3.288V5.045V417.63355.25°C115.27V
632.118A6.016A6.026A1.985A449.55489.092%735 RPM15.4 dB(A)40.60°C0.991
12.135V4.990V3.284V5.034V504.59755.86°C115.17V
737.534A7.018A7.042A2.190A524.47488.327%1325 RPM31.4 dB(A)42.34°C0.991
12.133V4.986V3.279V5.019V593.78757.82°C115.17V
842.959A8.034A8.062A2.395A599.41687.492%1960 RPM41.4 dB(A)43.07°C0.992
12.128V4.981V3.275V5.006V685.11259.02°C115.16V
948.809A8.539A8.586A2.400A674.43686.791%2310 RPM45.1 dB(A)44.06°C0.992
12.126V4.977V3.271V4.998V777.07960.62°C115.16V
1054.388A9.058A9.085A3.011A749.28485.960%2320 RPM45.2 dB(A)45.87°C0.993
12.127V4.973V3.268V4.977V871.66162.27°C115.15V
1160.564A9.067A9.093A3.015A824.13584.992%2320 RPM45.2 dB(A)47.30°C0.993
12.126V4.970V3.265V4.970V969.65865.69°C115.15V
CL10.099A12.013A12.004A0.004A100.75784.378%560 RPM10.5 dB(A)43.09°C0.973
12.145V4.998V3.290V5.101V119.41255.37°C115.21V
CL261.936A1.005A1.002A1.001A764.30986.243%2320 RPM45.2 dB(A)46.36°C0.993
12.125V4.982V3.279V5.037V886.23162.78°C115.16V

Load regulation on the +12V rail is very tight. It's a little looser on the minor rails, but still satisfactory. Only the 5VSB rail comes close to a 3% deviation, so it could be improved upon. When it comes to efficiency, the 80 PLUS Gold specification requires at least 87% efficiency with 20% and 100% of this PSU's max-rated capacity, and 90% efficiency under 50% load. As you can see, the first requirement is met. The PSU comes close at 50% load. However, under full load, there is a >1% difference compared to the desired 87%. As always, though, we run our tests at much higher ambient temperatures than the 80 PLUS organization's unrealistic 23°C levels.

The fan profile gets aggressive once the load and operating temperatures get too high. In our opinion, a larger fan and proper fan profile would solve this problem, enabling the same airflow at lower rotational speeds. Since a 140mm fan is out of the question, Seasonic could try using a 130mm fan like EVGA does with its G3 models.

MORE: Best Power Supplies

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This thread is closed for comments
7 comments
    Your comment
  • none77
    Thank you for the detailed review.
    In the transient response test
    Advanced Transient Response at 50 Percent – 200ms
    the +3.3 pass.
  • BugariaM
    As always, here are the most detailed reviews on the PSU.
    Thank you and keep it up!

    The only thing that is not quite clear to me. What is the criterion for voltage drop in % to get PASS/FAIL in "Advanced Transient Response Tests"?

    You declare that:

    "In all tests, we measure the voltage drops." The voltages should remain within the ATX specification's regulation limits. "

    For ATX 2.2 we have:

    12v - 10%
    5v - 5%
    3.3v - 5%
    5VSB - 5%


    However, looking at your reviews, there are often situations where, at <5%, the power supply gets the FAIL mark and vice versa, some at >5% receive PASS

    Why is this happening?
  • BugariaM
    Sorry, a typo
    Of course for 12v - 5%
  • Aris_Mp
    the limit is 5% however the voltage rails of the PSUs' under test in the majority of cases aren't at the nominal voltages, but higher, so even with 5% deviation voltages go don't bellow the limits that the ATX spec sets (11.4V, 4.75V, 3.14V). Only if a rail goes below those voltage levels it fails. The 5% is just an indication that the ATX provides to specify the voltages above.
  • BugariaM
    Now everything became clear to me.
    Thank you.
  • fredlaso
    Dell Inspiron 5675 Desktop, PSU (power supply unit), upgrade. Would this PSU compatible with Dell Inspiron 5675 Desktop. It came with 460W I would like to replace it with PSU between 650 to 750W. I tried at Dell forums but cannot get a clean link which one would be compatible.

    I would greatly appreciate if someone could help me out. Thank you kindly in advance:

    http://en.community.dell.com/support-forums/desktop/f/3514/t/20019321?pi21953=1#21018407
    http://en.community.dell.com/support-forums/desktop/f/3514/p/20024419/21031446#21031446

    System Comp,:
    Compatible Power Supply needed for Inspiron 5675 Gaming Power Supply
    Specs:

    AMD Ryzen 7 1700X 3.4GHz Octa-Core Processor
    8GB 2400MHz DDR4 RAM
    1TB 7200 RPM Hard Drive
    AMD Radeon RX 580 8GB GDDR5 Graphics Card
    DVD+RW Drive
    Dual Band WiFi 802.11ac + Bluetooth 4.1
    Windows 10 Home (64-bit)
    460 Watt Power Supply w/ Polar Blue LED
    Includes: Dell KB216 Wired Keyboard + Dell MS116 Wired Mouse
    Ports:
    6x USB 3.0
    1x USB 3.1 Type-C Gen 1
    2x USB 2.0
    1x Audio Combo Jack
    1x 3-in-1 Media Card Reader
    1x P/S 2
    1x 7.1 Channel Audio Out
    Expansion Slots:
    3x 3.5" bay
    2x 2.5" bay
    2x PCIe x1
    2x PCIe x16

    http://en.community.dell.com/support-forums/desktop/f/3514/t/20019321?pi21953=1#21018407
    http://en.community.dell.com/support-forums/desktop/f/3514/p/20024419/21031446#21031446
  • paulinosaka
    My Seasonic Platinum began failing under load after only 10 months. Paid cash here in Japan at Joshin - couldnt find reciept - honestly never thought I would need it ever. Seasonic would not help me.?
    REPLY