[R-390] R-390 (non A) power plug.

Tue, 9 Apr 2002 17:05:56 -0400

In shipboard electronics, there is a chassis ground which is grounded to
the hull of the ship.  The AC is distributed without reference to
ground.  You will measure about 65 Volts each leg to ground on a ship.
The reason for this is for battle damage.  If the ship suffers battle
damage and one leg of the single phase AC distribution becomes grounded,
there is no harm done.  The electrician will recognize this with their
ground isolation checks and repair the damaged distribution circuit.
The chassis ground is a safety ground.  In shore based electronics, you
could connect the non fused side of the power to ground with out problem
because neutral and ground are tied together at only one point (in the
distribution panel). Again chassis ground is safety ground. Neutral and
ground are two completely different legs at the equipment.  You can
cause some pretty dangerous situations by tying neutral and ground
together at the equipment.  I think that it is even against the
electrical code.

I spent 22 years of my life in the submarine force protecting you from
the evils of communism.

73 

Glenn 
WB4UIV

-----Original Message-----
From: [email protected] [mailto:[email protected]]
On Behalf Of Jim Temple
Sent: Tuesday, April 09, 2002 4:15 PM
To: [email protected]
Subject: Re: [R-390] R-390 (non A) power plug.

Thanks for the insights.  The only unanswered question is the grounding.

Within the cable housing that attaches to the radio are:

1.  Post "C".  This, according to the schematic, goes to the radio
electrical ground.
2.  Inside the connector housing, attached to the interior wall of the
housing, is a post with nothing attached to it.  I would assume that if
this
was attached to the outlet ground, it would provide a ground path to the
radio frame.

I have a curious mind, so I began thinking.......(watch out!!).

The power outlet ground, on a R-390A, is attached directly to the radio
frame. At least with mine this is so.  On the R-390, it seems that there
are
two paths to ground the radio.  1.  Post "C" of the power connector, and
2.
The radio frame.

I would assume that both are, practically speaking, the same.  So
attaching
to one or the other would accomplish the same purpose.  On the other
hand,
attaching to both, at the same time (within the housing), would probably
accomplish the same chore, or could there be possible ground loops
associated to grounding to both the radio electrical ground (power plug
post
C) and the frame ground at the same time??  Also, within the attaching
housing, the ground could be put in series or parallel  (One ground wire
attaching both points, or one wire branched to each post separately.

My experience says that multiple grounds can introduce unwanted
feedback.
Hence the importance of lead dress and routing.

Am I being too persnikity here, or is this a valid question??

Jim

----- Original Message -----
From: "Roy Morgan" <[email protected]>
To: "Jim Temple" <[email protected]>; <[email protected]>
Sent: Tuesday, April 09, 2002 3:30 PM
Subject: Re: [R-390] R-390 (non A) power plug.

> At 02:28 PM 4/9/02 -0400, Jim Temple wrote:
> >My new r-390 (NON-A)
> >
> >I have obtained a length of 3 wire and am installing it now.
>
> I assume you mean a three wire line cord with a grounded plug.
>
> >1.  Does it matter which lead, hot or common, is attached to F101?
>
> YES, it matters.
>
> >  Would it
> >be best to wire the hot (black) wire to  post "D", which is attached
to
> >F101, for purposes of efficient fuse protection?
>
> SAFE is the word not "efficient". The hot wire (black in US Standard
> cables) goes directly to the REAR terminal of the fuse holder (through
the
> line filter in the case of R-39x radios).  This does two things:
>
>   1) Reduces to the minimum the amount of line voltage exposure inside
the
> radio after the fuse blows.
>   2) Protects you (to some degree) from contacting the line voltage as
you
> replace the fuse.
>
> >2.  Would the power plug ground (green) best be utilized by attaching
it
to:
> >     a.  Post "C"?
>
> Yes, (I assume contact C is the one going to ground..)
>
> >     b.  The housing ground post?
>
> Do you mean the threaded center mechanical clamping post?  NO.  Do not
> depend on that for grounding.. do not use it.
>
> Roy
>
>
> - Roy Morgan, K1LKY since 1959 - Keep 'em Glowing!
> 7130 Panorama Drive, Derwood MD 20855
> Home: 301-330-8828 Work: Voice: 301-975-3254,  Fax: 301-948-6213
> [email protected] --
>
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>

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