donec said:
In DC circuits the negative is considered return or ground and is most likely connected to the earth ground in the brick along with the metal chassis of the AAO case.
Thank you for the reply.
This seemed plausible, but I used the multimeter to check continuity & can confirm
neither of the 2 DC output connections are connected to the earth.
I gather some computer PSUs have RFI filtering capacitors connecting both live & neutral to earth.
Hipro quote earth leakage current figures for some of their other supplies, so that suggests they may do this.
If anyone has pulled one apart or has a circuit diagram it would be nice to know.