MSI MPG A750GF Power Supply Review

MSI did a far better job than Gigabyte in its PSU products, but is this enough?

MSI MPG A750GF
(Image: © Tom's Hardware)

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Primary Rails And 5VSB Load Regulation

The following charts show the main rails' voltage values recorded between a range of 40W up to the PSU's maximum specified load, along with the deviation (in percent). Tight regulation is an important consideration every time we review a power supply because it facilitates constant voltage levels despite varying loads. Tight load regulation also, among other factors, improves the system’s stability, especially under overclocked conditions and, at the same time, it applies less stress to the DC-DC converters that many system components utilize.

Load regulation is tight on all rails.

Hold-Up Time

Put simply; hold-up time is the amount of time that the system can continue to run without shutting down or rebooting during a power interruption.

The hold-up time is way lower than 17ms and, to make matters worse, the power ok signal is inaccurate. It's been a long time since we encountered a PSU with a "fake" power ok signal. 

Inrush Current

Inrush current, or switch-on surge, refers to the maximum, instantaneous input current drawn by an electrical device when it is first turned on. A large enough inrush current can cause circuit breakers and fuses to trip. It can also damage switches, relays, and bridge rectifiers. As a result, the lower the inrush current of a PSU right as it is turned on, the better.

The inrush current is at normal levels with both 115V and 230V input. 

Leakage Current

In layman's terms, leakage current is the unwanted transfer of energy from one circuit to another. In power supplies, it is the current flowing from the primary side to the ground or the chassis, which in the majority of cases is connected to the ground. For measuring leakage current, we use a GW Instek GPT-9904 electrical safety tester instrument.

The leakage current test is conducted at 110% of the DUT's rated voltage input (so for a 230-240V device, we should conduct the test with 253-264V input). The maximum acceptable limit of a leakage current is 3.5 mA and it is defined by the IEC-60950-1 regulation, ensuring that the current is low and will not harm any person coming in contact with the power supply's chassis.

MSI MPG A750GF

(Image credit: Tom's Hardware)

Leakage current is low. 

10-110% Load Tests

These tests reveal the PSU's load regulation and efficiency levels under high ambient temperatures. They also show how the fan speed profile behaves under increased operating temperatures.

Swipe to scroll horizontally
Test12V5V3.3V5VSBDC/AC (Watts)EfficiencyFan Speed (RPM)PSU Noise (dB[A])Temps (In/Out)PF/AC Volts
10%4.424A1.99A1.975A0.985A75.00587.034%71120.140.72°C0.959
12.069V5.027V3.341V5.077V86.17945.45°C115.18V
20%9.870A2.987A2.965A1.184A149.96990.585%71320.241.09°C0.978
12.063V5.024V3.339V5.07V165.55746.21°C115.18V
30%15.671A3.486A3.461A1.383A224.97991.509%71420.241.49°C0.981
12.056V5.021V3.338V5.063V245.85547.28°C115.18V
40%21.486A3.986A3.957A1.583A300.07491.637%71520.241.77°C0.982
12.048V5.019V3.336V5.056V327.45948.02°C115.18V
50%26.925A4.985A4.949A1.783A374.70391.352%71820.342.72°C0.979
12.041V5.017V3.335V5.049V410.17349.25°C115.18V
60%32.393A5.985A5.941A1.984A449.63690.83%72120.443.1°C0.978
12.034V5.014V3.333V5.041V495.02950.1°C115.18V
70%37.869A6.987A6.935A2.186A524.57789.506%110633.443.18°C0.978
12.027V5.011V3.331V5.033V586.07850.67°C115.18V
80%43.422A7.991A7.93A2.288A599.79188.787%138239.743.83°C0.98
12.018V5.008V3.329V5.028V675.54251.99°C115.18V
90%49.316A8.494A8.415A2.39A674.80788.147%172245.044.97°C0.981
12.011V5.005V3.327V5.023V765.54754.56°C115.18V
100%55.209A8.998A8.93A2.492A749.94487.409%172345.046°C0.983
12.004V5.002V3.326V5.016V857.97456.21°C115.18V
110%60.780A10.003A10.018A2.494A824.9886.526%172445.046.8°C0.984
11.997V4.999V3.324V5.012V953.4557.68°C115.18V
CL10.116A14.393A14.314A0A121.3184.282%72620.744.31°C0.973
12.069V5.017V3.332V5.085V143.93349.69°C115.2V
CL20.116A21.911A0A0A111.39982.263%73120.943.1°C0.974
12.078V5.02V3.337V5.094V135.41850.19°C115.19V
CL30.116A0A21.749A0A73.99676.773%71520.241.98°C0.96
12.073V5.027V3.338V5.082V96.38351.43°C115.19V
CL462.424A0A0A0.001A749.8688.203%172345.044.02°C0.983
12.012V5.013V3.335V5.078V850.15455.27°C115.18V

The PSU delivers full power and 110% of its maximum rated capacity at 47 degrees Celsius without any problems. The APFC converter's performance is low, though.

20-80W Load Tests

In the following tests, we measure the PSU's efficiency at loads significantly lower than 10% of its maximum capacity (the lowest load the 80 PLUS standard measures). This is important for representing when a PC is idle with power-saving features turned on.

Swipe to scroll horizontally
Test12V5V3.3V5VSBDC/AC (Watts)EfficiencyFan Speed (RPM)PSU Noise (dB[A])Temps (In/Out)PF/AC Volts
20W1.231A0.497A0.493A0.196A20.00470.649%70920.037°C0.825
12.066V5.032V3.345V5.097V28.31540.28°C115.19V
40W2.708A0.696A0.691A0.295A40.00282.313%70619.837.94°C0.919
12.070V5.03V3.343V5.094V48.59741.52°C115.19V
60W4.187A0.895A0.888A0.393A60.00186.209%70820.038.38°C0.947
12.069V5.028V3.343V5.091V69.642.31°C115.18V
80W5.663A1.094A1.086A0.491A79.96988.138%70820.039.51°C0.96
12.067V5.028V3.342V5.088V90.73143.84°C115.18V

The efficiency is decent under light loads. 

2% or 10W Load Test

From July 2020, the ATX spec requires 70% and higher efficiency with 115V input. The applied load is only 10W for PSUs with 500W and lower capacities, while for stronger units, we dial 2% of their max-rated capacity.

Swipe to scroll horizontally
12V5V3.3V5VSBDC/AC (Watts)EfficiencyFan Speed (RPM)PSU Noise (dB[A])Temps (In/Out)PF/AC Volts
1.064A0.246A0.246A0.042A15.07766.033%68819.120.15°C0.779
12.037V5.028V3.342V5.102V22.83323.2°C115.15V

The PSU cannot pass the 70% mark with 2% of its maximum power, load. 

Efficiency & Power Factor

Next, we plotted a chart showing the PSU's efficiency at low loads and loads from 10 to 110% of its maximum rated capacity. The higher a PSU’s efficiency, the less energy goes wasted, leading to a reduced carbon footprint and lower electricity bills. The same goes for Power Factor.

This is an efficient platform on all load ranges but super light ones, where it cannot deliver more than 70% efficiency, as the ATX spec requires. 

5VSB Efficiency

Swipe to scroll horizontally
Test #5VSBDC/AC (Watts)EfficiencyPF/AC Volts
10.1A0.51W75.895%0.066
5.1V0.672W115.18V
20.25A1.275W79.008%0.147
5.097V1.614W115.18V
30.55A2.801W80.232%0.253
5.091V3.491W115.18V
41A5.083W78.224%0.353
5.081V6.498W115.18V
51.5A7.607W78.107%0.407
5.07V9.739W115.18V
62.501A12.625W75.781%0.464
5.049V16.66W115.18V

The 5VSB rail should be more efficient. 

Power Consumption In Idle And Standby

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Mode12V5V3.3V5VSBWattsPF/AC Volts
Idle11.103V5.023V3.338V5.103V0.0570.006
114.31V
Standby0.0460.004
114.31V

Vampire power is low. 

Fan RPM, Delta Temperature, And Output Noise

All results are obtained between an ambient temperature of 37 to 47 degrees Celsius (98.6 to 116.6 degrees Fahrenheit).

(Image credit: Tom's Hardware)

(Image credit: Tom's Hardware)

The fan speed profile could have more operation modes, under high operating temperatures, for lower noise output.  

The following results were obtained at 30 to 32 degrees Celsius (86 to 89.6 degrees Fahrenheit) ambient temperature.       

(Image credit: Tom's Hardware)

(Image credit: Tom's Hardware)

At normal operating temperatures, close to 30 degrees Celsius, the PSU is silent up to 490W loads. With 20-30W more, though, it enters the 30-35 dBA range and with more than 610W noise output exceeds 40 dBA. 

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Aris Mpitziopoulos
Contributing Editor

Aris Mpitziopoulos is a Contributing Editor at Tom's Hardware US, covering PSUs.