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From: wtm@neoucom.UUCP (Bill Mayhew)
Newsgroups: sci.electronics
Subject: Re: Neutral-Ground Shorts
Message-ID: <608@neoucom.UUCP>
Date: Tue, 9-Jun-87 21:36:24 EDT
Article-I.D.: neoucom.608
Posted: Tue Jun  9 21:36:24 1987
Date-Received: Sun, 21-Jun-87 06:04:45 EDT
References: <820@sdcc12.ucsd.EDU>
Organization: Northeastern Ohio Universities College of Medicine
Lines: 28
Keywords: AC power, neutral-ground
Summary: Ethernet transciever should be isolated


It is difficult to troubleshoot the ethernet problem without a some
more detailed information.  The co-ax cable for the ethernet
system should only be attached to an earth ground at a single point
on the cable.  Being grounded at only one location prevents
currents from circulating in the shield of the cable and thus
inducing noise.  Normally, the transciever units that tap the cable
are optically and/or transformer isolated to prevent multiple
grounds from being formed.

I`d suspect that if the interface you have has a transciever box
that clamps on the cable, that there is something wrong with the
cable that connects the interface with the cable tap transciever.
Carefully check that the cable shield is intact.  Most of the
problems that I have seen are caused by a problem in the cable
between the interface and the transciever tap module.

One last idea is to make sure that the box on the cable tap
transciever is properly put together.  Sometimes nylon screws and
washers, etc. are used to prevent a ground from being fromed
inadverntantly between the ethernet cable and the PC.

Hope this gives you some ideas...

Bill
NEOUCOM
Division of Basic Medical Sciences
(wtm@neoucom.UUCP)