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From: z-80@othervax.UUCP (Grant Bonnell)
Newsgroups: net.micro.atari16
Subject: Re: HELP!  520ST parallel printer port doubles characters?
Message-ID: <810@othervax.UUCP>
Date: Thu, 28-Aug-86 09:38:08 EDT
Article-I.D.: othervax.810
Posted: Thu Aug 28 09:38:08 1986
Date-Received: Sat, 30-Aug-86 03:12:23 EDT
References: <1310@watdragon.UUCP>
Reply-To: z-80@othervax.UUCP (Grant Bonnell)
Distribution: net
Organization: Philips Information Systems - St. Laurent  P.Q., Canada
Lines: 21

In article <1310@watdragon.UUCP> you write:
>I just bought a db25->centronics connector to hook up my ST to an old
>Seikosha GP-100A printer
>Unfortunately, characters sent from the ST arrive ddoouubblleedd at the
>printer.

I have also experienced this problem and determined that it was due to
a difference in potential between the ground at the connector of the atari
and that of the printer.  This causes noise on the signal lines and produces
the effect you mention.  A temporary solution is to ensure that one of the
two cable ends is NOT connected to the chasis ground.  This problem may stem
from the fact that your equipment is not properly grounded.  Are you certain
that the outlets into which your equipment is plugged are grounded?  For
example in my house (built about 30 years ago) I discovered that even though
the wall sockets were the grounded type (presumably installed by some
previous owner) the ground screw was not connected to anything, since
the house was wired with only two conductor cable.  I hope this helps.


Grant Bonnell
!philabs!micomvax!othervax!z-80