Emu XL-7 & MP-7 User's Group

WEsley opined:
 
<<<Ground hum sucks.  not to mention, they say somewhere between 1 in 5 or 1 in 10 outlets is
wired improperly.  apparently black, which is usually ground, on a normal US outlet is hot, white
is neutral, and green is ground.  so naturally people can get confused.  


     Black is usually ground?  Not in the US.  At least not in house wiring.  Or perhaps that's
what you were saying and I misunderstood your writing.  In electronics wiring yes, black is
usually ground.  In electrical wiring, black is always hot.


<<If anyone has a killer ground hum that you just can't shake it's possible your building isn't 
grounded properly.  You can check behind that plate on your circuit breaker, there should be an
actual wire there.  I've heard of homes not having them.  Also, sometimes they don't bury the
grounding rod as deep as they should.  I forget how deep it's supposed to go.>>

     You don't need to take off the plate, as it won't really tell you anything.  Sometimes an
outlet does have a grounding wire hooked up to it, other times the metal wall box is grounded via
the steel conduit that the wire runs through (less common).  Even if it does have the grounding
wire, that doesn't mean that it's hooked up to anything.  And even if you do have the black wire
going to hot (the smaller of the two prongs) and the white wire going to neutral, sometimes Joe
Homeowner has rewired things using the wrong color of wire.  The small tester that Steve mentioned
is great for figuring this stuff out.  Also useful is a small circuit tester (voltmeter) that can
be picked up for around $10.  You should always get 110 or so volts when testing the two spade
jacks, you should also get the same voltage when testing the hot with the third jack, the so
called grounding jack.

     The codes vary from county to county as to what is kosher for grounding rods stuck in the
earth.  It depends on how dry your environment is for one.  Sometimes the rod needs to be 8 or 10
feet long and located at least a foot away from the house.  This last requirement is so that the
eaves of the house don't keep the soil around the grounding rod too dry and thus make the
grounding connection less effective.  In some counties, it is enough to attach your house ground
to a metal cold water pipe (NOT a gas pipe).  Elsewhere, this is discouraged because sometimes the
metal pipe switches to plastic before entering the ground.

     Also ground loops are sometimes caused by hooking up various pieces of gear to different
outlets that are on different circuits.  Alternately, the wiring in your house may have been done
in a cattywompus way that actually creates ground loops.  This is not as common, though it does
come up from time to time.  I'm not sure if the Hum Eliminators fully get rid of that last
problem, as I've never had a chance to try them out.  I do know that when I rewired my house, all
the radio programs that used to come through the wiring depending on which room I set my gear up
in, all disappeared with the new wiring layout.

     Stephen





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