27-12-2011, 04:36 PM
Hello Rob, as mentioned in one of my previous posts I am not a qualified electrician, but appart from the normall precautions when servicing stuff containing voltages/currents that have the potential to kill then I have always regarded the protective earth as supplied by the electricity distributor as my true safety earth so all the equipment on my bench wether it be receiver or test gear or any combination of either/or have their chassis connected to this same earth, that being the supply earth ie all the chassis are are at the same 0 volts potential so to speak.
Anything that has the means of producing a floating chassis rail on my bench is a no no.
Ok... confession time... I do not have an isolating transformer at present, hence that is why I am extra cautious as regarding earthing especially considering the age and condition of some of the kit that ends up on the bench, in particular old power supplies with "y" configured mains filter caps or transformers that are prone to leakage.
I have B40D receiver that occasionaly trips the RCD on the supply, it does it because the filter caps. are on the way out and the fact that I earthed the receiver to the suppliers protective earth, if they totally break down then the trip will cut out perminantly, if the receiver was not earth connected the chassis could then become live with respect to earth under that fault condition and thus present a potential shock hazzard irespective of wether a supply RCD is fitted or not.
When I do obtain a suitable Isolating transformer I will connect it like it says in the guide posted as I have worked in workshops in the past where that method was used. Plus when using test equipement there is always a common earth for referencing.
Lawrence.
Anything that has the means of producing a floating chassis rail on my bench is a no no.
Ok... confession time... I do not have an isolating transformer at present, hence that is why I am extra cautious as regarding earthing especially considering the age and condition of some of the kit that ends up on the bench, in particular old power supplies with "y" configured mains filter caps or transformers that are prone to leakage.
I have B40D receiver that occasionaly trips the RCD on the supply, it does it because the filter caps. are on the way out and the fact that I earthed the receiver to the suppliers protective earth, if they totally break down then the trip will cut out perminantly, if the receiver was not earth connected the chassis could then become live with respect to earth under that fault condition and thus present a potential shock hazzard irespective of wether a supply RCD is fitted or not.
When I do obtain a suitable Isolating transformer I will connect it like it says in the guide posted as I have worked in workshops in the past where that method was used. Plus when using test equipement there is always a common earth for referencing.
Lawrence.
