Xref: utzoo comp.dcom.modems:5030 comp.mail.uucp:3899
Path: utzoo!utgpu!jarvis.csri.toronto.edu!clyde.concordia.ca!uunet!yale!eagle!flinton
From: flinton@eagle.wesleyan.edu
Newsgroups: comp.dcom.modems,comp.mail.uucp
Subject: Re: an echo on the line
Message-ID: <5464@eagle.wesleyan.edu>
Date: 6 Jan 90 21:54:40 GMT
References: <1990Jan2.235724.7287@utzoo.uucp>
Lines: 26

In article <1990Jan2.235724.7287@utzoo.uucp>, henry@utzoo.uucp (Henry Spencer)
 writes:
> A little while ago ... everything we sent got echoed!  ... I suggested
> a close inspection of the RS232 cable.  Turned out the cable was half-
> unplugged at the modem end, and this was the problem.  
  Not long ago I found a 4 ohm quasi-short between lines 2 and 3 (TxD and RxD)
in a modem cable I was trying (unsuccessfully :-) !) to use.  Nothing BUT
echo!  Long cable for a short run, so I cut it in half.  One end good,
other end still showing 4 ohms.  Slit and removed the molding from the 
connector on the bad half, pried open the shield thereunder, snipped the
lead to pin 2: STILL 4 ohms twixt pins 2 and 3!  After further disassembly:
  Turns out the cable manufacturer had used crimp pins and stranded wire
(nothing unusual there) and _one_strand_ that should have been crimped with
its mates to pin 2 at one of the connectors was brushing up instead against
pin 3, deep within the plastic pin-cushion sandwich held together by those
press-fitted D-rings.  Snipped that strand off, reassembled all (not forgetting
to rejoin the severed ends of the lead to pin 2) and ... well, two perfectly
usable half-cables needing DB-25's at one end each.             | still just |
  Maybe I'll wire one of 'em up as a nul-modem ...    -- Fred   | a babe in  |
                                                                | the woods! | 
Fred E.J. Linton  Wesleyan U. Math. Dept.  649 Sci. Tower  Middletown, CT 06457

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