IBM Selectric Manual

b. Adjust the negative-5 latch stop screw so that the
negative-5latch (Fig. 53) wi II reset simultaneously
as the check pawl drops into the notch on the check
ratchet at the rest position.
Cycle Shaft
Latched
At
cc::=-----
Adjust Stop Screw --- __ ~
Negative Latch Bail
FIGURE 53. Negative 5 Latch Stop Screw
+5
The negative-5 latch controls the position of the
negative latch bai I during zero and all positive ro-
tate selections. Changing the latch ad justment
causesthecoarsealignmentofthe zero and all posi-
tive rotate selections to change equally with respect
to the negative selections. No change is fe It in the
coarse alignment of the negative rotate selections
when the negative-5latch adjustment is altered be-
cause the latch is out of the system during all nega-
tive selections (Fig. 54).
Considering the balance lever to be properly ad-
justed, the effects ofthe negative-5latch adjustment
on the system can be explained by the following:
From the rest position the amount of movement in
the negative direction given to the rotate bellcrank
is fixed because the negative latch bai I moves from
the high point of the negative cam to its low point.
From the rest position the amount of movement in
the positive direction given to the rotate bellcrank
can be increased or decreased by changing the nega-
tive-5 latch adjustment. In other words, when the
machine is at rest the negative-5 latch bai I is rest-
ingonthehighpointofthe negative-5 cam. When-
ever a no-rotate or positive selection occurs, the
negative-5 latch bail is allowed to follow its cam
towards
the low point until it is restricted by the
negative-5Iatch. This small increment of negative
motion to the negative -5 latch bai I during a no-
rotate or po~itive selection causes the positive mo-
tion to be reduced by an equal increment. There-
+4
+3
+2
+1
o
7.
fore I the ad justment ofthe negative latch can change
the balance of motion between positive and negative
selections. Even though it is possible, it is not per-
missible to use the negative latch adjustment for
balancing purposes. The negative latch should al-
ways be adjusted for the proper reset clearance.
This allows the system to operate with optimum lever-
age loads in both positive and negative selections.
Balancing between positive and negative should al-
ways be accomplished by adjusting the balance lever.
NOTE: Figure 54illustrates how the coarse align-
ment detenting would change at the typehead if only
the negative-5 latch adjustment were maladjusted
on a machine. It is possible for this same detenting
pattern to show upon a machine that has the correct
negative-5 latch adjustment but other adjustments
maladjusted. For this reason it is best to adjust the
negative latch as specified in the adjustment rather
than byadjusting it while observing the effects that
the adjustment change wi II produce at the type head .
Rotate Arm
Vertical - With the typehead removed and
the machine half-cycled using the letter Ill", adjust the
rotate link so that the poi nt at the top of the rotate arm
is 15/32
11
from the machine sideframe. The compensator
roller should be 1/16" from the top of the slot when this
adjustment is made.
#1 Scribe Line
~
FIGURE 55. Rotate Link Adjustment Measurement
-1
-2
-3 -4
-5
FIGURE
54. Excessive Negative 5 Latch Clearance
19

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