LA36 various responses - test-drb@ccmp.vtda.org

27 Dec 2002

One person interested in 20 ma LA36's, and I think an answer in error from
Don Maslin.  Thanks for the information on the 20 ma question Kevin and Larry

I'm not sure if these units are 20ma loop - but from their history I'd
expect them all to be the same.  The plug on the connecting cable is a DB25
female, and the wires go to pins 1 through 7.  Models are;  Datacom 400 (the
one which may work), 2 Datacom 1200's, and 1 Decwriter III.  Does the pin
connection help with the 20ma question, or is there a simple test I can make
on the lines?  I'm not sure from Kevin Hardy's letter if one could just
change the wiring - it sounds like it, but these may be OK already.  I tried
to see if I could tell what the output driver is (as per Larry's comment),
but the board isn't very easy to see.  There appears to be an output IC
labelled 7550 - is this a valid TTL number?

Don Woods

Message: 3
...
 From: Barry Moyer &lt;barry.moyer(a)pason.com&gt;
To: &quot;&#39;cctalk(a)classiccmp.org&#39;&quot; &lt;cctalk(a)classiccmp.org&gt;
Subject: DEC LA36
Date: Tue, 24 Dec 2002 09:08:19 -0700
Reply-To: cctech(a)classiccmp.org

Don,

I am in Calgary and I have a newer LA36, but I am looking for another older
LA36 with a 20mA loop connection.  You can contact me at 'iamvirtual at
hotmail dot com'  (replace at with @, dot with .)

Thanks

Barry
 ...
...

Message: 9
From: "Fred Flintstone" &lt;iamvirtual(a)hotmail.com&gt;
To: cctalk(a)classiccmp.org
Subject: Re: DEC LA36 units
Date: Tue, 24 Dec 2002 10:46:02 -0900
Reply-To: cctech(a)classiccmp.org

Don,

I am currently looking for an older LA36 which has a 20mA connection (I need 
it to connect to my ancient PDP-11s).  Do you know the model numbers for the 
LA36?

Thanks.

--Barry

.

Message: 15
Date: Tue, 24 Dec 2002 15:59:09 -0800 (PST)
From: Don Maslin &lt;donm(a)cts.com&gt;
To: cctalk(a)classiccmp.org
Subject: Re: DEC LA36 units
Reply-To: cctech(a)classiccmp.org

...
 No Barry, sorry, but Dec printers are outside my area
of knowledge.

						- don Message: 4
Date: Thu, 26 Dec 2002 09:39:19 -0700
From: Kevin Handy &lt;kth(a)srv.net&gt;
To: cctalk(a)classiccmp.org
Subject: Re: DEC LA36
Reply-To: cctech(a)classiccmp.org

Barry Moyer wrote:

...
 Don,

I am in Calgary and I have a newer LA36, but I am looking for another older
LA36 with a 20mA loop connection.  You can contact me at 'iamvirtual at
hotmail dot com'  (replace at with @, dot with .)

I believe that the 20ma current loop was available for all the LA36's.
It was just a different cabling option, bit a 'new' or 'old' version
thing.
You could buy the 20ma current loop with your LA36, or later as
an option to change an existing one from RS232 to 20ma.

Message: 13
From: "Truthan,Larry" &lt;truthanl(a)oclc.org&gt;
To: &quot;&#39;iamvirtual(a)hotmail.com&#39;&quot; &lt;iamvirtual(a)hotmail.com&gt;
Cc: &quot;&#39;cctalk(a)classiccmp.org&#39;&quot; &lt;cctalk(a)classiccmp.org&gt;
Subject: DEC LA36 Decwriter II
Date: Thu, 26 Dec 2002 16:42:02 -0500
Reply-To: cctech(a)classiccmp.org

I  have  the engineering prints  in the  LA 36  Decwriter II

LA36 (MPC5)  sheet  5 of 8 shows 20 ma RECIEVE on J3 pin 7(+)  and Pin 3(-)
bridged by  a 3.3 volt  zener D4 746A feeding  a 4N26 (E43) opto-isolator
which  drives a MXAA05 (Q4) driver transitor which has its collector on J4
pin 2 "S.I." (serial in)

20 ma  TRANSMIT is  on J3 Pin 5(+) and  Pin 2(-).  These  pins  are bridged
by a 1N4004 diode D6.  This  diode  also is  parallel to the
emitter/collector of Q2, an A05. which is  driven by another 4N26
opto-isolator (E47).  S.O. is  J4 pin 4.  It is  driven  by  a 7404 inverter
(E62)-(Input is 7404 pin 3 connected to the diode cathode of the
opto-isolator, output is 7404 pin 4, which connects  directly to J4 pin 4,
"S.O." serial out)

Sincerely  

Larry Truthan