Transformer question (only slightly OT)

[Tony Duell]

> 
> Is one side of your mains grounded?  Here in the US, the most common

Yes. The 'neutral' side of our mains is connected to ground at some point 
(normally at the secondary of the last distribution transformer -- note 
that over here a single transformer supplies many houses, we don't have 
the equivalent of your 'pole pigs'). 

But no device may assume that the neutral side of the mains is 'safe' to 
touch. It muse be inaccessible without the use of the tool. Single-pole 
switches and fuses must be in the live (hot) side of the mains. It is 
against the rules to put a protective device (fuse/breaker) in  the 
neutral side at all unless you use one where a fault on that side will 
turn off the live as well (e.g. a double pole circuit breaker, but not 2 
independant single pole ones). Oh yes, the outer cap of an ES or similar 
light bulb is the neutral side.

> distribution is a 120-0-120v distribution transformer with the center tap
> connected to ground.  So, for common 120v wall receptacles, one side  (in

Yep. My Tekky curve tracer's manaul gives transformer primary winding 
connection diagramss for 3 configurations : 115V, 230V with one side 
grounds, and 230V with the centre tap grounds. I believe it's to reduce 
noise, etc, it's not any safety problem

> addition to the grounding prong) is grounded.  I've popped the GFI on my
> workbench outlet on several occasions--in every case, it involved a "hot
> chassis" piece of equipment.  Sparks are pretty, but I'll take the
> inconvenience, thank you.


Well, when working on a live chassis set, or on the mains side of an 
SMPSU, I use an isolating transformer. It means I can connect the 'scope 
to points on the device without damage or blowing the breaker.

-tony