[R-390] Ham Shack Grounding Help!!!!

[Barry Hauser]

Hi Kim:

That 60 volts from the chassis to plumbing is probably the leakage from the
line filter caps.  There was a great deal posted on this.  They will cause a
ground falt interrupter to trip.  There are a number of workarounds, if your
electrician wants to put one in your shack -- like removing the filter, etc.

The PC power supply is a likely suspect, however there are a number of other
variables in PC construction:

The cases keep getting cheaper and cheaper -- imagine $30 for an ATX case
with power supply and two fans -- what can it be made of -- tin can stock
complete with coating/varnish.  I've seen three basic formats -- tin can
frame and back with painted steel U shaped cover, same with removable sides
and back, and variants with plastic sides with either thin metal shields
inside or just conductive paint.  You have to make sure somewhere on the
mating surfaces the paint or coating was removed or masked, otherwise a
panel can radiate rather than shield.

The motherboard and how it's mounted is another thing.  There should be at
least one metal screw making contact with a ground pad on the MB which then
goes into a metal standoff.  If the MB was installed only with plastic
standoffs, it isn't grounded properly.  Motherboards also vary -- number of
layers with the better ones having ground/shield layers.

Also, the main ground point for the whole business is the PS to case
connection.  They usually mount with four mounting screws, but both the PS
and case frame have that coating.  It's possible to have a bad ground if
it's just depending on the heads of those screws.

So, you might check that out -- but, sounds like you've got no real ground
at all at your outlets.  Your radio wouldn't tingle with 60 vac if it has a
proper 3 wire power cord going into a correctly wired and grounded outlet.

Be especially careful until all that is fixed -- and then still be careful
after that.

You should have your whole electrical system checked out -- as the
electrician will, no doubt, recommend.

Barry

----- Original Message -----
From: "Kim Mackey" <mackeyka@mac.com>
To: <r-390@mailman.qth.net>
Sent: Thursday, June 20, 2002 11:21 PM
Subject: Re: [R-390] Ham Shack Grounding Help!!!!


> I have received lots of good info that I can use to help eliminate my
noise
> problems.  I was out all day today so did not get to follow up on any of
> this.  Yesterday however I did do one check and it did not look good.
There
> is 60 v. from the chassis of my radio to the cold water pipe.  Not good at
> all.  I am going to get an electrician in here as soon as possible to see
> what we are going to have to do to fix that.
>
> Tomorrow I will post info about the ham shack set up what computer I'm
using
> and such, to narrow down what is going to be my best approach.  One thing
> I'm pretty sure of; the power supply in the computer may be the culprit on
> the Windows machine.  I get that noise even with the monitor off.  On my
mac
> system I get the noise from the monitor (it's not a mac monitor).  The
noise
> it generates if at different freqs. And I can fix it by switching monitor
> resolutions.  But the noise from the PC is on all bands and top to bottom
of
> the KC.
>
> Kim
> KC9BZL
>
> Sent using the Entourage X Test Drive.
>
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