Your power supply appears to be missing the Y capacitor which will make it more difficult to measure the output noise (the 2V you are seeing is almost surely not real). It does have what look likes a nice common-mode choke and X capacitor(s).

The purpose of this capacitor is to conduct some of the 67kHz switching noise out to the earth terminal. It must be a safety rated capacitor designed for Y use. Don't just stick any old cap in there- this is a safety issue.

To get a better measurement, try grounding the supply output to earth and using a differential measurement on the output terminals (A-B with two scope probes). Just grounding the output deliberately (not through the scope probe) should help.

Your power supply appears to be missing the Y capacitor which will make it more difficult to measure the output noise (the 2V you are seeing is almost surely not real). It does have what look likes a nice common-mode choke and X capacitor(s).

The purpose of this capacitor is to conduct some of the 67kHz switching noise out to the earth terminal. It must be a safety rated capacitor designed for Y use. Don't just stick any old cap in there- this is a safety issue.

To get a better measurement, try grounding the supply output to earth and using a differential measurement on the output terminals (A-B with two scope probes). Just grounding the output deliberately (not through the scope probe) should help.