Exploratorium looking 4 working ASR-33 or KSR - test-drb@ccmp.vtda.org

13 Jun 2011

Message: 13
Date: Sun, 12 Jun 2011 19:14:49 -0700
From: Eric Smith <eric at brouhaha.com>
Subject: Re: Exploratorium looking 4 working ASR-33 or KSR
To: General Discussion: On-Topic and Off-Topic Posts
    <cctalk at classiccmp.org>
Cc: ronh at exploratorium.edu
Message-ID: <4DF57299.4090403 at brouhaha.com>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed

On 06/12/2011 19:14:39, Eric Smith wrote:

...
 On 06/12/2011 03:47 PM, Bruce Damer wrote:
  Team if anyone on this list has a working
ASR/KSR-33 they would like
 to donate for an excellent exhibit at the Exploratorium, please
 contact Ron below, see note...

 Your Name: Ron Hipschman
 Your Email address: ronh at exploratorium.edu

 Do you guys have a functioning RS-232 teletytpe (ASR-33 or KSR-33)
 kicking around that might want to be donated to the Exploratorium for
 a possible exhibit?

 Ron Hipschman
 I've seen a lot of model 33 Teletypes, and I've never yet seen one that
is RS-232. They are almost all current loop.  I don't recall seeing any
mention of an RS-232 option in the manuals, although that may have
existed as a third-party modification. 
...
 IIRC, the model 40, 42, and 43 machines offered RS-232.
 The 40 is a CRT
terminal with an optional printer, and the 43 and 43 are 5-level and
ASCII (respectively) versions of a compact dot matrix printing terminal. 
Oh ye of little faith.  Tymshare made LOTS of RS232 capable ASR-33's.
They had a mod kit that they used along with the OEM call control unit.
It came in several models.  The early one (circa 1968) had a small transformer (to make
the proper voltages) and a control board with a relay to turn on the motor when CD (pin 8)
became true.  It preserved the Local/Off/Line switch function (the rotary switch on the
call control unit).  A later version used push buttons on the cover plate that goes over
the CCU section of the ASR/KSR-33.  They replaced the Line/Off/Local rotary switch on the
"front panel" that was subject to knob breakage (usually a panicked service
call).  The front escutcheon that had the hole for the Line/Off/Local switch was replaced
with a nice Tymshare enhanced logo snap on plate that looked nice.

My (at the moment lost or trashed) ASR-33 I did my own RS-232 conversion.  It consisted of
taking taps off of the transformer of the CCU (to get the other voltage) and including a
nice solid state relay to do the "Carrier Detect" function for motor control. 
It required only a couple of transistors for the receive (RS232 to 20ma CL) and resistor
tree for the other direction.  Having a RS-232 capable ASR33 was a real nice thing to have
when most of the connectors were DB-25's.

On another note:  I do have a couple of old DECWRITERS.  An LA-30 (modified for lower
case) and a larger wide carriage one that I don't remember the model number (upper and
lower case as well).

Ah yes, fun from the past....  