Ripple Measurements

You will see the ripple levels we measured on the P1700-MA-EU's rails in the following table. The limits are, according to the ATX specification, 120 mV (+12V) and 50 mV (5V, 3.3V, and 5VSB).

Ripple suppression at +12V was excellent and good enough at 5V and 3.3V. All went well until 5VSB failed to comply with the ATX spec in the CL1 test. Very light loads apparently have 5VSB register a ton of ripple, while normal loads won't cause ripple to shoot out of spec.

Ripple at Full Load

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

Ripple at 110% Load

Ripple at Crossload 1

Ripple at Crossload 2

Ripple during 5VSB tests

As you can see in these shots, ripple was way too high in the first two 5VSB tests with 0.1 A and 0.25 A. Ripple in the other two tests, with 1 A and 3 A, is much lower and well within spec.