To learn how we measure ripple, please click here.
The following table includes the ripple levels we measured on the rails of the Zalman ZM750-EBT unit. The limits, according to the ATX specification, are 120mV (+12V) and 50mV (5V, 3.3V and 5VSB).
Ripple suppression clearly isn't among this PSU's strengths. The 5VSB rail failed not once or twice, but five times in keeping its ripple within limits. And the 5V rail went over 50mV in our full load and overload tests. We also measured close to 70mV at +12V under full load. That's a high reading, given that we don't want to see anything above 50mV, especially from PSU that utilizes a modern platform. Finally, the 3.3V rail performed significantly better, though it also has a problem with ripple control and isn't able to match the competition. Sirfa should revise this platform and fix its ripple performance.
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 0.01V/Div (each vertical division/box equals 0.01V) as the standard for all measurements.