Teletype Model 28 Mark I, Mark II, Mark III Differences

Mark I (Navy TT-47/UG) to Mark II (Navy Type TT-47A) differences

The following components in Teletypewriters TT-47A/UG, TT-48A/UG, TT-69A/UG, and TT-70A/UG differ from the corresponding ones in Teletypewriters TT-47/UG, TT-48/UG, TT-69/UG and TT-70/UG.

(1) POWER DISTRIBUTION PANEL SB-154A/UG.- This component differs from SB-154/UG principally in that the connectors on the ends of the cables leading to the Keyboard and to the Automatic Typer have been changed. Therefore, it cannot be connected to the MX-1114/UG Keyboard or to the MX-1115/UG Automatic Typer.

{2) KEYBOARD MX-1114A/UG.-This component differs from MX-1114/UG in several respects. It has a 20 terminal receptacle, whereas the MX-1114/UG has a 14 terminal receptacle. Thus this component cannot be connected to a SB-154/UG Power Distribution Panel. The spring powered throwout mechanism has been removed from the MX-1114A/UG clutch. The position of the repeat key has been shifted to the right and the repeat mechanism has been redesigned. Several changes have also been made in the adjustments, and in the lubricating procedure.

(3) AUTOMATIC TYPER MX-1115A/UG .- This component differs from MX-1115/UG in several major respects and in numerous minor details. Since the changes in adjustments are many and varied, the adjustment requirements specified in Section 7 of this instruction book must be adhered to. The MX-1115A/UG has a 20 terminal receptacle, whereas the MX-1115/UG has a 14 terminal receptacle. Consequently, this component cannot be connected to a SB-154/UG Power Distribution Panel. The MX-1115A/UG has a new main shaft, and a redesigned selector mechanism with an improved method for orienting the range finder. The ribbon feed mechanisms have been revised to include an improved slack take up feature and improved feed pawl adjustment. The range of the automatic carriage return-line feed arm on the spacing drum has been increased to accommodate a maximum of 85 characters per line. Also, several ratchet teeth have been removed from the spacing drum to prevent over spacing in the event of spacing clutch stop failure or spacing suppression failure. Changes in the lubrication procedure are few.

Mark I Keyboard - LK1, LK2? 

2-row connector on keyboard base
IMG_3160.JPG (4644861 bytes)
LESU with 2-row connectors
IMG_3156.JPG (4929123 bytes)
Wiring Diagram
IMG_3161.JPG (2291999 bytes)
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Mark II Keyboard - LK3, LK4, LK5, LK7 

- some Mark II keyboard parts drawings

Keyboard transmitter
IMG_3153.JPG (5421348 bytes)
Keyboard mechanism protector bar
IMG_3154.JPG (6503873 bytes)
Keyboard cover (hood) top view
Mark III above, Mark II below
IMG_3165.JPG (3540064 bytes)
Keyboard cover (hood) bottom view
Mark III above, Mark II below
IMG_3167.JPG (4455035 bytes)

Mark III Keyboard - LK6, LK8 and on

keyboard transmitter
IMG_3149.JPG (7080849 bytes)
No protector bar Keyboard cover (hood) top view
Mark III above, Mark II below
IMG_3165.JPG (3540064 bytes)
Keyboard cover (hood) bottom view
Mark III above, Mark II below
IMG_3167.JPG (4455035 bytes)

Mark I Printer - LP1, LP2? - almost the same as Mark II?

slotted ribbon carriage rail (black)
slotted typebox carriage rail (steel)
(note that this is a flat piece with larger holes than Mark II)
IMG_3207.JPG (4944343 bytes)
Type box carriage rail A-1324
Teletype Part 150844
IMG_3209.JPG (4709980 bytes)
2-row electrical connector
IMG_3157.JPG (4935355 bytes)
2-row connector J-1301
Teletype Part 151815
IMG_3210.JPG (3720405 bytes)

Mark II Printer - LP3, LP4, LP5, LP6, LP7, LP8, LP9 

- some Mark II printer parts drawings

Left side of printer
IMG_3150.JPG (2976827 bytes)
solid ribbon spool retainer clips
IMG_3163.JPG (2987514 bytes)
slotted ribbon carriage rail (black)
slotted typebox carriage rail (steel)s
IMG_3172.JPG (4709704 bytes)
slotted ribbon carriage rail (black)
slotted typebox carriage rail (steel)
IMG_3205.JPG (4222234 bytes)

Mark III Printer - LP10 and on

Left side of printer
IMG_3148.JPG (3374819 bytes)
wire ribbon retainer clips
IMG_3164.JPG (5107358 bytes)
round hole ribbon carriage rail (black)
unslotted typebox carriage rail (steel)
IMG_3176.JPG (4536422 bytes)
Hybrid or updated? Mk II solid ribbon retainer clip and Mk II left side with Mk III round hole ribbon carriage rail (black) and Mk III unslotted typebox carriage rail (steel)
IMG_3208.JPG (6876327 bytes)