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Path: utzoo!mnetor!seismo!cmcl2!phri!roy
From: roy@phri.UUCP (Roy Smith)
Newsgroups: comp.periphs
Subject: RS-232 connector flame!  Manufacturers, listen up!
Message-ID: <2539@phri.UUCP>
Date: Sun, 14-Dec-86 13:39:07 EST
Article-I.D.: phri.2539
Posted: Sun Dec 14 13:39:07 1986
Date-Received: Tue, 16-Dec-86 18:59:04 EST
Reply-To: roy@phri.UUCP (Roy Smith)
Distribution: world
Organization: Public Health Research Inst. (NY, NY)
Lines: 62


                    ___  ______________
     male thread   <   >             ^
          \------> <   >             |       Socket for attachment screw,
                   <   >             |       typical RS-232 connector
                   |   |             |
                ___|   |___ _____    |       Note: all dimensions approximate
                |         |   ^      |             not to scale
                |   ___   |   |      |             typical material: brass
   hex shaped   |  <   >  |  3/16   3/8
   exterior --> |  < ^ >  |   |      |
                |__< | >__| __v______v_
                     /
    female thread---/

	You've all seen the little gizmo described above.  Most of the
RS-232 connectors on terminals, computers, and modems have one of them on
each side.  Weighs about a gram.  These are where you are supposed to screw
in the little screws that hold the cable from falling out.  The problem
comes when you try to take the cable off a few months (or years) later.

	You take a little screw driver and turn the screw in the cable
connector.  To your horror, you find that the screw isn't unscrewing from
the threaded hole in the above described socket, but the whole socket is
turning!  Why should this happen?  Because, the socket is simply held in by
a nut and (sometimes) a lock-washer on the male end -- it's a toss-up which
threaded joint will go first (and don't give me any lip about tightening
the outside screws too tight!).

	Sometimes, the socket comes out and you can just screw it back in;
not so terrible, but rather a pain in the ass.  Worse is when the little
nut on the back falls off and drops down inside the piece of equipment --
now you've got this bit of metal rattling around inside your computer (or
terminal, or whatever) wreaking havoc -- a fried CPU board isn't worth
saving a few cents on a connector!

	What's the solution?  The short-term solution is every time I have
a piece of equipment open for whatever reason, I zap those nuts with a blob
of epoxy.  The real solution is for the people who make these things to
come up with a better way of attaching the sockets.  Remember a couple of
weeks ago I was singing the praises of the lowley ADM-3?  Guess what?
Along with everything else the ADM-3 had going for it, it had screw sockets
that didn't fall off -- they were molded into the plastic connector shell.
Why can't other manufacturers do something like that?  A keyed shaft, or a
bit of factory-applied potting compound would probably work just as well.

	People I've seen do it right: Lear Siegler, Hewlett-Packard (not
surprising; I disagree with a lot of what HP does with computers, but they
sure do know how to build things), U.S. Robotics, Graph-On.

	People I've seen do it wrong:  Digital, Emulex, Able, C. Itoh (they
get the special prize for shipping sockets with metric threads!), Sun,
Epson, NEC, Multi-Tech, IBM (surprising; I disagree with almost everything
IBM does with computers but generally have great respect for the way they
build equipment), Volker-Craig, Texas Instruments, Advanced Electronic
Design, GTCO, Summagraphics, Apple.
-- 
Roy Smith, {allegra,cmcl2,philabs}!phri!roy
System Administrator, Public Health Research Institute
455 First Avenue, New York, NY 10016

"you can't spell deoxyribonucleic without unix!"