Quote Originally Posted by Voicecoil View Post
......That's why SMPS engineers tend to work with one hand behind their back I guess!

Seriously though, the danger isn't that great as to get a shock off an isolated supply you'd basically need to be touching something live with one hand and something neutral with the other, which is likely a smaller risk than touching something live and leakage to earth via feet etc.. And of course as part of the procedure I've always gone through when working in such a way, you do a check that there's mains earth continuity through the iso. transformer, so that in this case the machine chassis is properly earthed.
I could have misunderstood but I think kitwin was making the point that, even with a good chassis earth, you will not notice if you have a short from line or neutral to the chassis. So, if you then touch chassis and live you will get a belt the RCD might not protect you from.