IBM Selectric Maintenance Manual page 43

With the damper spri ng stop a II the way up, the damper
spring should not be completely collapsed. Check and
adjust the rotate spring to satisfy both conditions.
NOTE: Lower damper spring stop to bottom before pro-
ceeding with sequence.
CAUTION: The damper spring method is only usable
when it is impossible to obtain a spring scale.
NOTE: The accuracy given to the next seven coarse
alignment adjustments determines the "band width" (de-
tenting variation) of the rotate system. Each one of
these seven adjustments contributes to the band width in
a different manner. Generally, it takes experience in
making each adjustment to learn how much accuracy is
needed to end up with an accumulated band width which
is acceptable. The band width of the rotate system
should never exceed .020" nor should any extra time be
spent in trying to obtain one any less than .0lD".
References wi II be made to 2 different methods of ob-
taining a zero rotate character. These methods can
be defined as:
Latched Home - zero rotate with NO plus or minus
rotation. I/O Home - zero rotate with BOTH plus
5 and minus 5 rotation.
6. Rotate Selector Latches
a. Form tlie stop lugs above the pOsitive rotate selector
latches (Fig. 70) so that the latches will reset si-
mu
taneous
y
(under the latch bail) just as the cycle
clutch check pawl drops into the ·notch on the check
ratchet at the rest position.
NOTE: The adjustment theory under "tilt selector
latches" also pertains to the rotate selector latches.
Form These Lugs
I
,
'"
\~-
- - - - - - - / " " \ '
-
----~_i....b
FIGURE 70. Rotate Selector Latches
b. Adjust the negative-5 latch stop screw so that the
negative-5 latch (Fig. 71) will reset simultaneously
as the check pawl drops into the notch on the check
ratchet at the rest positi on.
2-20
Cycle Shaft
Latched At
Negative Latch Bai I
FIGURE 71. Negative 5 latch Stop Screw
The negative-5 latch controls the position of the
negative latch bai I during zero and all positive ro-
tate selections. Changing the latch adjustment
causes the coarse alignment of the zero and all posi-
tive rotate selections to change equally with respect
to the negative selections. No change is felt in the
coarse alignment of the negative rotate selections
when the negative-5 latch adjustment is altered be-
cause the latch is out of the system during all nega-
tive selections (Fig. 72).
Considering the balance lever to be properly ad-
justed, the effects of the negative-5 latch adjust-
ment on the system can be explained by the follow-
ing: From the rest position the amount of movement
in the negative direction given to the rotate bell-
crank 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 move-
ment in the positive direction given to the rotate
bellcrank can be increased or decreased by changing
the negative-5 latch adjustment. In other words,
when the machine is at rest the negative-5 latch
bai I is resting on the high point of the negative-5
cam. V/henev6i
Ci
zero rotate or positive 5e lecti on
occurs, the negative-5 latch bail is allowed to fol-
low its cam towards the low point until it is re-
stri cted by the negative-5 latch. This small incre-
ment of negative motion to the negative-5 latch
bai I during a zero rotate or positive selection causes
the positive motion to be reduced by an equal incre-
ment. Therefore, the adjustment of the negative
latch can change the balance of motion between
positive and negative selections. Even though it is
possible, it is not permissible to use the negative
latch adjustment for balancing purposes. The nega-
tive latch should always be adjusted for the proper
reset clearance. This allows the system to operate
with optimum leverage loads in both positive and
negative selections. Balancing between positive
and negative should always be accomplished by ad-
justing the ba lance lever.
NOTE: Figure 72 j((ustrates how the coarse align-
ment detenting would change at the type head if only
the negative-5 latch adjustment were maladjusted
on a machine. It is possible for this same detenting
p"attern to show up on a machine that has the correct
negarive-5 latch adjustment but other adjustments