IBM Selectric - Page 53

7.
Considering the ba.lance lever to be properly ad-
justed, the effects of the negative -5 latch 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 bail is rest-
ing on the high point of the negative-5 cam. When-
ever a no-rotate or positive selection occurs, the
negative-5 latch bai I 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 bail during a no-
rotate or positive selection causes the positive mo-
tion to be reduced by an equal increment. There-
fore, 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 per-
missible to use the negative latch adjustment for
balancing purposes. The negative latch should al-
ways be adjusted for th~ 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 accompl ished by adjusting the balance lever.
NOTE: Figure 117 illustrates how the coarse align-
ment detenti ng wou I d change at the typehead if on I y
the negative-5 latch adjustment were maladjusted
on a machine. It is possible for this same detenting
pattern to show upon a mach i ne that has the corre ct
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 will produce at tbe typehead.
References wi II be made to 2 di fferent methods of
obtaining a no 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 andminus
5 rotation.
Rotate Arm Vertical - With the typehead removed and
the machine hal f-cycled to an upper case zero rotate
character (latched home) adjust the rotate link so that
the point 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.
The adjustment sets up a vertical condition for three
points in the rotate arm, the center of the pulley, the
rotate arm pivot point, and the rotate I ink connection.
With the rotate arm vertical at a half-cycled zero rotate
position, the leverage within the rotate arm will be the
same for positive and negative movements of the arm.
2-35
The adjustment can be measured- using the #1 scribe line
on the Hooverometer handle as illustrated in Fig. 118.
The scribe line measurement makes allowance for the
thickness of the compensator damper spring.
#1 Scribe Line
FI GURE 118. Rotate Link Adjustment Measurement
NOTE: The eccentric stud at the top of the rotate arm
should be turned all the-way to the left at this point to
prevent interference with subsequent adjustments.
8. Preliminary Typehead Homing - Half cycle the machine
under power using an upper case zero rotate (latched
home) character. Check detenting, if in correct notch
of typehead preliminary adjus~ent of .010
11
to .020"
does not appl y. Go on to next ad justment.
If detent is in wrong typehead notch, then loosen screw
in bottom of rotate pulley and sl ip type head so the de-
tent will enter .010" to .020" from the center of the
detent notch on the negative side of the notch when
head play is lightly removed in the negative direction
(Fig. 119).
.~~
~/ I I
( I
FIGURE 119. Type Head Homing
Head Play
Removed
Clockwise
(Negative)
The mai'n purpose of this preliminary homing adjustment
istoaid the Customer Engineer in making the rest of the
coarse al ignment adjustments. It places the typehead
in approximatel y the correct position so that its rotation,
for a given selection, may be easily measured and used
as a tobl in making the next four adjustments. A fter com-
pleting this sequence of adjustments the prel iminary hom-
ing adjustment may have to be refined.
NOTE: Be sure to maintain .002" to .004
11
end play in
the rotate shaft when making this adjustment. Also, make
sure that the compensator roller is 1/16
11
from the top of
the slot.