Adam,

On Thu, 5 Jan 2006 16:45:26 -0500, M. Adam Davis wrote:

> Double check your power stips and house wiring.

Already done - there is excellent Earth continuity from the end of the lead just before it enters the power 
block (I used an Earth Fault Loop Impedance meter - the thing professional electricians use - and the 
impedance measures 0.7ohm).

I measured the resistance from the Earth pin on the input of the power block to the 0V connection on the DC 
side, and they are isolated.  So the Earth pin is present, but not connected inside!  Which probably means 
there are capacitors from the Phase and Neutral to the 0V output, forming a high impedance voltage divider, 
giving the results I have.  I tried measuring the current that it can supply into as near a short circuit as 
my meters can provide, and it's about 0.25mA.  As I said, uncomfortable but not painful...

I suspect this is a unit built down to a price in the Far East, and I don't imagine the compliance markings 
are worth much - as it's not double-insulated (and it isn't marked as such) then it must be Earthed to comply 
with the various standards, not to mention UK import laws.  I need to take it back and get a refund, methinks!
 
> Usually this is due to bad ground.  Worse is when someone at a school
> cut off the ground wire of the AV cart.  Plug it in backwards, and
> it's ok.  Now connect the RF to the school cable system, and suddenly
> everyone else sees 120V on the ground of the cable system.

I'm really glad of the design of plug/sockets over here - it would be almost impossible to do that (sockets 
have shutters that rely on the Earth pin to open them).

Cheers,


Howard Winter
St.Albans, England


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