IBM Selectric Service Manual

12.
Torque Bar Overthrow Stud (Fig. 170) - With the tab
cam on its high point, form the upright lug on the LH
end of the torque bar for a clearance of .001" - .010"
between this lug and the overthrow stud.
Tab Torque Bar
Interlock Switch
Trigger
FIGURE 170. Torque Bar Overthrow Stud (Late)
TABULATOR MECHANISM (EARLY)
I . Tab Lever Stop - Form the stop on the escapement bracket
(Fig. 171) to obtain .001" to .003" clearance between
the vertical lug on the tab lever and the backspace pawl
when
the tab lever is at rest and the backspace pawl is
fully seated in its rack.
//
/'
Tab Lever Stop
-- .....
/" "
/
'I
---
Tab Lever ~
Backspace Pawl ~ ~/"--.,,I-- .001" to .003"
FIGURE
Ill. Tab Lever Stop
This
small clearance insures that the backspace pawl will
be allowed to bottom in its rack and that a minimum a-
mount of tab lever motion will be required to remove
both
the backspace and escapement pawls from thei r
racks during a
tabulation operation.
2. Tab Lever Pawl - Adjust the pawl forward or back on the
tab
lever so that the tip of the pawl clears a SET tab stop
by
.035" to .045" with the tab lever at rest (Fig. 172).
FIGURE 172.
Tab Lever Pawl
2-50
The adjustment of the tab lever pawl has an effect on the
amount of overlap between the .tab stop and the pawl tip
in the active position. It also directly affects the pawl
clearance during tabulation. Unless the tab lever pawl
is properly adjusted, correct pawl clearance cannot be
obtained.
The adjustment of the tab lever pawl can be measured by
using the push-end of the large spring hook. The push-
end is approximately .035" thick.
3. Tab Rack - Adjust the tab rack left or right for a clear-
ance of .005" to .020" between the tip of the tab lever
pawl and a set tab stop with the tab lever latched out.
This adjustment is made by the tab rack bushing on the
RH end of the tab rack. The clearance may be observed
by
holding the carrier and latching the tab lever out.
NOTE: The head of the tab rack bushing should clear
the tab rack plate by approximately 3/32" when the ad-
justment is complete. (Fig. 173).
Tab Rack Plate
Tab Stop Tab Rack
Adjust Tab Rack
•
Bushing
-- --
Tab lev", ~:005" fa .020"
Bushing
4.
Tab Pawl
FIGURE
173. Tab Rack Bushing
The tab rack adjustment sets up a condition whereby the
escapement pawl will be released into the escapement
rack at the right time to safely engage the correct tooth.
If the tab rack were too far to the left, the tab lever
would contact the set tab stop sooner and release the es-
capement pawl 'into the rack earlier than it should. The
pawl could enter the wrong escapement rack tooth and
stop the carrier one space to the left of the desired stop-
ping point. The carrier could stop one space too far to
the right if the tab rack were adjusted too far to the
right.
Pawl Clearance - The upright lug of the tab latch shou Id
be formed forward or back so that the tip of the escape-
ment pawl clears the escapement rack teeth by .005" to
.010" when the tab lever is latched to the rear.
The adjustment insures that the escapement pawl wi tI re-
enter the rack quickly to minimize the chances of en-
tering the wrong rack tooth. If excessive clearance is
present, it is also possible that the tab keylever and as-
sociated parts might not have enough throw to positively'
latch the tab lever each time.

IBM Selectric Specifications

General

Type	Electric typewriter
Introduced	1961
Keyboard Layout	QWERTY
Carriage Return	Electric
Manufacturer	IBM
Printing Technology	Typeball (golf ball)
Power Source	AC Power
Power Supply	120V AC