[GreenKeys] New to real Teletype

[Nick England]

Hi Trent - welcome to the wonderful world of real teletype.
The basic circuit is that the printer's selector magnets (solenoids)
are energized by 60ma current pulses on the serial line (loop
current).
The keyboard is usually wired in series with the selector magnets so
that when the keyboard interrupts the current loop the printer and
anything else in the loop responds. To make the KSR "talk to itself",
you need a source of 60ma current - this is accomplished with a 120v
dc loop supply in series with a 3000 ohm resistor. The reason for the
high voltage is that it is needed to kick-start the selector magnets
on each pulse.

So I assume the ST-6 has a built-in loop supply. And of course the
ST-6 will send signals on that loop when it is receiving something or
generating a test message. Some TU units have a built-in loop supply
and others don't, requiring an external supply.
(For that matter, some KSRs have a built in loop supply)

So basically you need just a loop supply to "talk to yourself" and a
TU to receive TTY over the air or over the internet.

Here's a link to my web page with tons of TTY manuals, etc.
http://www.navy-radio.com/manuals-ttycorp.htm
Here is a vintage guide to RTTY with helpful TTY info
http://www.navy-radio.com/manuals/tty/RTTY_Handbook_1982.pdf
and here is a helpful schematic for the 28KSR
http://www.rtty.com/development/teletype/model28KSR/wd2875.pdf
and associated wiring diagram
http://www.rtty.com/development/teletype/model28KSR/wd2874.pdf
Note that there were about a million ways to wire a teletype machine
even before a ham modified it....

A 28KSR manual that I like is this big (44MB) Navy one - it does a
pretty good job of explaining things
http://www.navy-radio.com/manuals/tty/tt47-93241.pdf

They are indeed marvelous machines - I started out 4 years ago with a
28ASR and said that's all I'll ever need/want. Now I have about almost
20 model 28 machines of various types running in the
basement.......with big thanks to all the helpful people on the list!

Good luck & Have Fun!

Nick England K4NYW
www.navy-radio.com


On Sun, Oct 18, 2015 at 6:33 PM, Trent Williams <tsdptsdp at icloud.com> wrote:
> Hello from KJ4KAF,
> Yesterday, I brought home a model 28 KSR.  The seller (ham operator) gave me a good demonstration of the printing function as a signal was fed from an ST-6. However, the keyboard function is not connected to anything it seems. The keys do function and there is mechanical action when a key is pressed.
>
> His signal feed line appears to bypass almost everything and connects directly to the 2 solenoids (wired in parallel). The line has around 65 ohms of resistance.
>
> Is there a way to have the machine print what I type? Is an ST-6 what I need as well?  My first goal is to receive anything I can find on the bands or the Internet. At some point, I would like to at least print what I am typing - will the right TU do this?
>
> This is the first teletype I have ever seen - what an incredible mechanical wonder this thing is!
> Today, I just signed up to join the email list.
>
> Thanks for any help understanding this, Trent
>
> Sent from my iPad.
>
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