[GreenKeys] Signal Line Connection - RS-232 Interface

[Clay Archer]

The shorting link is for half duplex operation with I/O on terminals 5 & 8.
Remove the shorting link for full duplex with send loop on terminals 5 & 6,
and receive loop 7 & 8.     When I got my 35 ASR it had been rewired
incorrectly and caused it to be looped in line mode.    A good schematic of
the ASR is available at https://www.blunham.com/Misc/ASR35/   The terminal
block is the one below where the power cord attaches (at least on my 35
ASR). 

 

There are several good designs for RS232 to 20ms current loop.    There is
one that uses two opto-isolators and has fewer parts, but the one you show
works well too. 

Clay

 

 

 

From: greenkeys-bounces at mailman.qth.net
[mailto:greenkeys-bounces at mailman.qth.net] On Behalf Of Ken Wiebe
Sent: Thursday, May 30, 2019 6:19 PM
To: Thomas Tillson via GreenKeys
Subject: [GreenKeys] Signal Line Connection - RS-232 Interface

 

As you may know, for the 33 ASR several people have designed and built
circuits to convert current loop to RS-232.  Example, I think Mike Douglas
may be a member of greenkeys and here is a link to his:

 

http://altairclone.com/teletype.htm

 

Question:

 

What about the 35 ASR?

 

I need to do this for the 35.  I couldn't find much online so I turned to
the 35 wiring diagrams in an attempt to find the signal line circuitry
equivalent to the 33.  On the 33, it's four pins on the P2 connector which
equate to the terminal strip pins 3, 4, 6, 7.

 

I think I found the relevant diagram for the 35, please see attached.
Something called "T" power terminal block, pins 5-8.

 

Anyone know where this is?

 

Sidenote:  See the note in the attd pic, "REMOVE LINK".  It looks like that
link sets up a loopback, right?  That may explain why my 35 seems always to
be in Local mode?

 

Anyway, I don't know where that "T" block is, and if you all could give me a
sanity check I'd appreciate.

 

Am I on the right track you think?

 

Thanks!

 

Ken

 

PS  I also attd Mike's schematic for the 33 version of the RS-232 adapter so
you can see what I'm making comparisons to

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