Saturday, August 25, 2018

Work on model 14, 15 and 19 teletype parts


Marc is in contact with a fellow YouTuber who does CNC work on gears to see if he can make a replacement for the motor pinion gear I would need to hit the standard 60 wpm transmission rate (about 6 1/8 rotation per second). This is achieved by taking the 1800 rpm synchronous motor, putting on a 9 tooth pinion gear and coupling that to a 44 tooth gear on the main shaft. 

I am also pursuing a possible source of another 14 TD which might have the right gears in place, but it will be a week or so before I know if this will pan out. 

We worked to get the wiring of Marc's TD correctly installed. Once that was completed and verified, he continued to install the labels, covers and other parts to finish this up. Next week he will run a test to transmit the contents of some test tapes to one of the model 15 printer units.


My model 15 teletype has a bent typebar for the letter Z which results in the letter printing faintly in the superscript area above the line of the other typed characters. This is due to a deformation of the shape of that typebar, which sits on the outside edge of all the typebars on the carriage. 

Z typebar prints too high compared to other letters
I can see from the rest position of the typebar that it is bent out of position. The typebar shape is complex, with several bends the ensure the typeface strikes right in the middle of the ribbon opening, flat and at the proper height. To fix the misalignment, I need to adjust several of the bends. I am studying and making a detailed plan for the bending necessary.

Leftmost (Z) typebar out of position

Ken and I began to install all the wiring, receptacles and switches into the desk today. Fortunately, the Teletype company drew up a wiring diagram, which is distinct from the more usual schematic. The wiring diagram shows each part in place with the actual wiring that is connected. This includes the jumpers that connect different terminals on the terminal blocks.

It goes so far as to identify the wiring bundles that are laced together with string - in one long group of wires there are several bundles. Each bundle runs to one or two receptacles and I can distinguish them by the number of wires hooked together. A circuit continuity tester gave me resolution to the individual wire in each bundle.

By the end of the day, I had two fuses and five receptacles fully wired, additionally I had four phone jacks wired but not fully verified. Ken had three switches on the front of the desk wired and the power lines installed through the flexible armored cable and

Finished wiring receptacles and fuses while the signal jacks at right are nearing completion
Power switches and one armored conduit installed, more to do on right
The wires from all these receptacles, fuses and switches run to five terminal blocks that connect together the 110VAC, 120VDC, send, receive and test lines. There are quite a few jumpers that run from one part of the terminal blocks to another part. Many of these are loose and have to be replaced as part of the wiring. I still have to install the metal stands that the five terminal blocks attach to, then complete the wiring.

Terminal blocks being wired and tested, but not yet mounted in place

Mike Albaugh brought over his typing reperforator. This is a unit that will take the incoming characters from the signal lines and punch them on 11/16" paper tape, using a chadless method that leaves the hole with a hanging chad.

In today's terms, because of elections, we think of chads as things that hang attached to the main paper, but the original terminology calls the completely removed circle of paper a chad and that chad falls into a waste chute. If the hole remains partially attached, it is called chadless by Teletype.

The reason that the hole is only perforated partially is to leave the paper in place since characters will be typed on the tape. If there were holes, the characters would be obscured by the holes. This way, you can read the typing on the paper tape but the pins in the Transmitter/Distributor will push the flap away and accurately detect where a partial hole was punched.

This unit has a selector unit and typebars, much like the model 15 printers we restored, but it is quite a bit less complex in many ways. No function box since actions like tab, carrier return or line feed don't make any sense when performed on paper tape. Instead a special character is typed that represents each of those functions. Thus, this machine only needs type bars to print all the letters, figures and control function characters.

When Mike got it wired up, he found that the selector mechanism was too gunked up to perform properly when we tested it. The motor and solenoids were moved and it was dunked in Simple Green to remove old lube. At the end of the day he began to remove, reassemble and lubricate parts of the typing and punching mechanism. It will take at least another session to get this working properly. 


  1. Hi Carl,
    Have you solved the problem of the bent typebar for the letter Z?
    How did you proceed?

  2. Hi Xavier

    That is an open task - once I got distracted with the AGC I didn't wrap up the TTY stuff. However, Marc has fixed some of his bent typebars on the model 19. It is just a matter of rebending the bar until its shape more closely matches its peer typebars. Small bend, check, iterate.