FSP Hydro PTM 650W PSU Review: Clean, Quiet Power for Mid-Range PCs

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Ripple Measurements

To learn how we measure ripple, please click here.

The following table includes the ripple levels we measured on the HPT650M’s rails. The limits, according to the ATX specification, are 120mV (+12V) and 50mV (5V, 3.3V, and 5VSB).

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10% Load28.8mV4.9mV4.7mV11.9mVPass
20% Load19.8mV4.6mV5.0mV13.8mVPass
30% Load17.5mV5.4mV5.4mV17.5mVPass
40% Load18.8mV5.5mV5.3mV22.4mVPass
50% Load19.7mV6.5mV5.6mV23.4mVPass
60% Load21.6mV7.1mV6.1mV17.3mVPass
70% Load21.6mV7.3mV6.6mV18.0mVPass
80% Load22.9mV8.3mV8.2mV16.0mVPass
90% Load23.8mV8.9mV8.6mV17.2mVPass
100% Load25.6mV8.9mV8.9mV19.6mVPass
110% Load26.9mV9.6mV9.6mV18.4mVPass
Cross-Load 119.0mV7.3mV9.3mV6.4mVPass
Cross-Load 225.9mV7.6mV5.7mV7.6mVPass

All of the rails deliver clean voltages. It is nice to see such good results from a power supply that doesn't rely on extra filtering capacitors in its cables.

Ripple Oscilloscope Screenshots

The following oscilloscope screenshots illustrate the AC ripple and noise registered on the main rails (+12V, 5V, 3.3V and 5VSB). The bigger the fluctuations on the screen, the bigger the ripple/noise. We set 0.01 V/Div (each vertical division/box equals 0.01V) as the standard for all measurements.  

Ripple At Full Load

Ripple At 110-Percent Load

Ripple At Cross-Load 1

Ripple At Cross-Load 2

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Contributing Editor

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