FSP Hydro PTM 750W PSU Review

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Efficiency, Temperature & Noise


Our efficiency testing procedure is detailed here.

Using results from the previous page, we plotted a chart showing the HPT750M's efficiency at low loads, and loads from 10 to 110 percent of its maximum-rated capacity.

The efficiency levels under normal loads are high enough. However, Aerocool's ACP-750FP7 is clearly ahead, particularly under light loads.

Efficiency At Low Loads

In the following tests, we measure the HPT750M's efficiency at loads significantly lower than 10 percent of its maximum capacity (the lowest load the 80 PLUS standard measures). The loads we dialed were 20, 40, 60, and 80W. This is important for representing when a PC is idle, with power-saving features turned on.

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Test #12V5V3.3V5VSBDC/AC (Watts)EfficiencyFan SpeedPSU NoisePF/AC Volts
11.212A0.492A0.469A0.195A19.62669.906%865 RPM25.2 dB(A)0.921
22.453A0.986A0.979A0.396A39.75480.980%865 RPM25.2 dB(A)0.963
33.695A1.477A1.482A5.031A59.83285.083%865 RPM25.2 dB(A)0.982
44.928A1.985A1.963A0.796A79.79386.996%865 RPM25.2 dB(A)0.989

Under light loads, the fan spins at its minimum speed.

With 20W load, efficiency is a hair away from 70%. It easily surpasses the 80% mark in the other three tests.

5VSB Efficiency

The ATX specification, along with CEC, ErP Lot 3 2014 and ErP Lot 6 2010/2013, states that 5VSB standby supply efficiency should be as high as possible, recommending 75 percent or higher with 550mA, 1A, and 1.5A of load. The PSU should also achieve higher than 75% efficiency at 5VSB under full load, or with 3A if its max current output on this rail is higher than 3A.

We take six measurements: one each at 100, 250, 550, 1000, and 1500mA, and one with the full load the 5VSB rail can handle.

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Test #5VSBDC/AC (Watts)EfficiencyPF/AC Volts

FSP equips its high-end offerings with efficient 5VSB circuits, and the HPT750M is no exception. It would be great to see other OEMs follow FSP's example when it comes to the 5VSB rail.

Power Consumption In Idle And Standby

In the table below, you'll find the power consumption and voltage values of all rails (except -12V) when the PSU is idle (powered on, but without any load on its rails), and the power consumption when the PSU is in standby mode (without any load, at 5VSB).

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Mode12V5V3.3V5VSBWattsPF/AC Volts

Vampire power is kept very low thanks to the SEN013DG, which disconnects the APFC converter when the PSU is in standby.

Fan RPM, Delta Temperature, And Output Noise

Our mixed noise testing is described in detail here.

The chart below illustrates the cooling fan's speed (in RPM), and the delta between input and output temperature. The results were obtained at 37°C (98.6°F) to 47°C (116.6°F) ambient temperature.   

The next chart shows the cooling fan's speed (again, in RPM) and output noise. We measured acoustics from one meter away, inside a hemi-anechoic chamber. Background noise inside the chamber was below 6 dB(A) during testing (actually it is much lower, but our sound meter’s microphone hits its floor), and the results were obtained with the PSU operating at 37°C (98.6°F) to 47°C (116.6°F) ambient temperature.

The following graph illustrates the fan's output noise over the PSU's operating range. The same conditions of the above graph apply to our measurements, though the ambient temperature was between at 30°C (86°F) to 32°C (89.6°F).

For the most part, the fan rotates at its minimum speed, making very little noise. Although there is no semi-passive mode, this is a very unobtrusive PSU. It's not the 750W category's quietest, but you'd have to be extra sensitive to noise if 25 dB(A) is too much for you. Finally, our sound measurement equipment didn't catch any coil whine.

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Aris Mpitziopoulos
Contributing Editor

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