Tabulator Set And Clear Mechanism - IBM Selectric Maintenance Manual

TABULATOR SET AND CLEAR MECHANISM
1. Tab Rack Bellcrank - Adjust the bellcrank (Fig. 158)
attached to the left end of the tab rack so that an unset
tab stop is centered between the tab lever pawl and the
tab set lug on the escapement bracket (Fig. 157). Latch
the tab lever to the rear to check this adjustment.
FIGURE 157. Tab Rack Bellcrank Adjustment
CAUTION: Be sure that the tab set and clear lever is
fully seated on top of the two pivot pins on the left side
of the powerframe.
2. Tab Set and Clear Link - Adjust the link so that the key-
button is vertical.
3. Set and Clear Arm Stops - Form the stop lugs on the set
and clear lever bracket (Fig. 158) so that they limit the
movement of the arm just as the tab stop fully reaches its
set or cleared position. A Iso, form the extensi on on the
rear stop lug so the tab set and clear arm cannot pivot
sideways out of engagement with the tab rack bellcrank.
II:S~_---
Be
Ilcrank
and C lear Arm
Upper Slot Edges
Should be Punched So That
The Link Cannot Accidentally
Disengage
FIGURE 158. Set And Clear Arm Stops
NOTE: On the early style tab set and clear mechanism
the stop lugs were anchored and adjusted by two screws
on the outsi de of the powerframe.
4. Tab Rack Brake - Adjust the tab rack brake so that the
tab rack will not flip past the rest position when released
from either a set or clear position. The tab rack must
return fully to the rest position when the keybutton is
2-47
released slowly. The brake is located just inside the
powerframe at the left end of the tab rack. The brake
should be formed, if necessary, to spring load the tab
rack toward the RH side of the machine.
CAUTION: The index detent lever will rest against
the tab rack with the platen removed. Be sure the lever
is clear of the tab rack when the brake adjustment is
checked.
5. Gang Clear Finger
FIGURE 159. Gang Clear Finger
a. Adjust the gang clear finger front to rear to obtain
.001" to .020" clearance (Fig. 160) between its tip
and the nearest tab stop when a II the tab stops are
set.
b. Form the end of the gang clear finger to obtain a
minimum of .001" clearance (Fig. 160) between the
gang clear finger and the tab rack tube. Check for
interference between the top of the gang clear finger
and the underside of the tab set spring.
FIGURE 160. Gang Clear
c. Check for a minimum of .001 "clearance (Figure
160) between lugs on the rear of the escapement and
backspace pawls and any set tab stop when the tab
rack is rotated to the clear position and the pawls
removed from the rack, as in a carrier return opera-
tion. If this clearance is not present, recheck tab
rack position and pawl clearance adjustments.
NOTE: It will not always be possible to clear a
single tab stop when two or more adjacent tab stops