Path: utzoo!utgpu!jarvis.csri.toronto.edu!cs.utexas.edu!samsung!munnari.oz.au!basser!usage!decus!heuer
From: heuer@decus.com.au (Powell HEUER)
Newsgroups: comp.sys.dec.micro
Subject: Printing - LA50 XON/XOFF problems
Message-ID: <20@decus.com.au>
Date: 20 Dec 89 19:21:07 GMT
References: <8912032300.AA02025@LANAI.MCL.UNISYS.COM> <847@tardis.Tymnet.COM>
Organization: DECUS, South Pacific Chapter
Lines: 19

In article <847@tardis.Tymnet.COM>, jms@tardis.Tymnet.COM (Joe Smith) writes:
> The usual causes of this (XON/XOFF problems) are:
>   1) The computer is not configured to respond to XON/XOFF from the printer.
>   2) The cable to the printer is defective, and not passing pin 2 back.
>   3) The motherboard in the printer has gone defective and transmits garbage.
> 
> Case #3 is what I see a lot of.

I have encountered another cause of similar problems.
Unlike most other printers/terminals, it seems that pins 1 and 7 on the RS232
interface (protective and signal grounds) are not tied together at the LA50
chassis.  I found this out the hard way with a faulty cable that had a break in
one of these (I can't remember which).  The symptom was that the printer could
receive and print text but XON/XOFF characters it sent were not received
correctly.

This lack of correct ground could also make the printer more susceptible to
interference and damage to the logic board - a contribution to some of your
case #3's?