So, I just built myself a little differential probe kitset to do "proper' ripple measurements with, and decided to test it on an Antec Basiq BP350 that I have just recapped.
I started with the 5vSB rail, and was getting some 200mV p-p spikes.
That's not good, obviously. But then I remembered the ATX guidelines about testing ripple... and that it requires capacitors (100nF and 10uF) across the probe.. so I added them.
That reduced the spikes to about 20mV which is obviously within the spec of 50mV.
Does this waveform look normal for a DM311 based 5vSB rail? Sorry for the photo quality, the camera refused to focus on the trace.
Ignoring the recommended probing setup, this means the 5vSB is genuinely generating 200mV p-p spikes when running. Is this normal? It is a flyback design. Do they just not care and assume that the motherboard filtering will take care of it? (which I suppose it must do, if the test set does.)
Or have I done something stupid? I did not use the isolation transformer on the PSU as I am using the differential probe, and the ATX spec diagram shows the PSU to be grounded, which it is.
There is no indication in the diagram as to whether the oscilloscope should be isolated or not. It recommends a Tek TDS460 which is a standard mains-powered bench-top CRO, so I assume not, and I did not isolate mine.
I started with the 5vSB rail, and was getting some 200mV p-p spikes.
That's not good, obviously. But then I remembered the ATX guidelines about testing ripple... and that it requires capacitors (100nF and 10uF) across the probe.. so I added them.
That reduced the spikes to about 20mV which is obviously within the spec of 50mV.
Does this waveform look normal for a DM311 based 5vSB rail? Sorry for the photo quality, the camera refused to focus on the trace.
Ignoring the recommended probing setup, this means the 5vSB is genuinely generating 200mV p-p spikes when running. Is this normal? It is a flyback design. Do they just not care and assume that the motherboard filtering will take care of it? (which I suppose it must do, if the test set does.)
Or have I done something stupid? I did not use the isolation transformer on the PSU as I am using the differential probe, and the ATX spec diagram shows the PSU to be grounded, which it is.
There is no indication in the diagram as to whether the oscilloscope should be isolated or not. It recommends a Tek TDS460 which is a standard mains-powered bench-top CRO, so I assume not, and I did not isolate mine.
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