1. Non-Overline for the Teletype Model 28

On a normal Teletype machine, when someone hits CR, the carriage will automatically come back but will not turn up a new line. This is a nice feature for RTTY Art but a real problem if you are trying to copy a weak signal and you are already receiving partially garbled text.

Fortunately, the Model 28 machines can be easily converted to avoid overlining. This change requires no new parts and can easily converted back to factory stock in a few minutes.

Here are the steps to make the change:

1. Remove the roll of paper

With the motor running, look at the top of the stunt box.

Hit the CR key and some slot will show activity. This should be slot 5, counting from right to left as you stand in front of the machine.

2. Hit the LF key and two slots should show activity. These should be slots 38 and 40, counting from right to left as you stand in front of the machine.
3. Leave slot 40 alone.

Remove the LP and take out the stunt box (after disabling all power).

Swap the universal code bars in slots 5 and 38 and reassemble the machine.

Now, when the CR key is pressed, nothing happens. When the LF key is pressed, both CR and LF occur at the same time.

You will still have to hit the CR key when you are transmitting. The CR character still needs to be sent to the distant machine. It may seem awkward to type the CR key and have nothing happen. But, the simplicity of this change, the fact that no additional parts are needed and that it works so well are huge benefits.

　

 

2. Automatic Carriage Return and Line Feed

The next step is to remove the stunt box and add the parts to slots 4 and 39. Before you do this, you will need to code the uncoded code bar by breaking off all of the tines except for one. This is going to look like a very strange code bar when you are finished. The one tine that remains is in the zero level, non-selected position. There is a good picture of the function bars and how they are coded along with an overview of the stunt box in the Teletype brochure that you can find here: http://www.rtty.com/development/books/stuntbox.pdf. This will take a while to download. Page 12 of 20 has a good picture of the code bars.

If you don’t have access to this document, break off all ten tines at the top of the code bar and three of the four tines at the bottom of the code bar. The one tine that remains is in the upper right quadrant of the four tines that are clustered together.

Once you have the slot parts and the code bar installed, and the stunt box and LP are all back in place, the checkout is pretty easy. First confirm that spacing over to the extreme right hand margin causes an automatic CR and LF. Then go back and count the exact point when this occurs. By standard, you should get 73 characters on a line an automatic return on character 74. If this is set correctly, you are finished.

To adjust the return character, locate the spacing drum and the five bolts holding the front and rear rings to the spacing drum. Going clockwise, you will see that the first, third and fifth are all round-head bolts. The second and fourth are hex-head bolts. You have to slightly loosen, but not remove, the first, second, third and fifth bolts to adjust the right hand margin adjustment. .Take a screwdriver and slightly move the rear ring that is attached to the spacing drum. Move the ring counterclockwise to lengthen the line length. You don’t have to move the ring very far so go slowly. Temporarily tighten the bolts that you loosened and try the line length test until you get the desired line length.