IBM Selectric Manual page 20

5.
Check the othertilt positions and then refine the homing
adjustment on the tilt selection that provides the least
amount of ri se to the rear of the tilt ring.
As a further check, remove the tilt ring play in the po-
sitive direction and observe the detent entry on the for-
ward side of the detent notch (Fig. 50B). The detent
should enter far down the forward slope of the detent
notch but not so far that it contacts the ti p of the tooth.
By homing the tilt ring off center, favoring the positive
side of the detent notch, a maximum amount of wear
potential is achieved.
Rotate Spring Tension - Adjust the rotate spring in the
rocker so that it will have 1-7/8 to 2 pounds tension
when the machine is half-cycled using a lower case "m"
(negative 5). The least amount of tension is present in
the spring when it is in this position. The type head must
be
removed when making this adjustment.
The rotate spring tension is adjusted by furning the spring
cage from the front (Fig. 50A). The cage can be turned
clockwise to increase the tension by pull ing the cage
toward the left with a spring hook. The spring drum
retainer automatically snaps into position to retain the
adjustment. If tension is to
be
decreased, the retainer
must
be
pulled forward to allow the cage to rotate counter-
clockwise. Care must
be
taken to decrease the tension
slowly so that the cage does not spin freely. Spring
damage could otherwise result.
FIGURE 51-A. Rocker Assembly
Tension of the spring is critical in that it must be prop-
erly balanced with the springs of the wear compensator.
Excessive tension will overload the levers system and
increase wear. Insufficient tension wi II not provide the
torque necessary for rapid lower case negative rotate
operations. It will also affect the wear compensator
operation ifthe tension is not sufficient to overcome the
compensator damper spring in the negative-5 position.
18
6.
The rotate spring tension should
be
measured with a spring
scale as indicated by Fig. 51 B. Using a lower case "m",
read the spring scale while slowly allowing the shift arm
to move intowardsitsstopscrew. The spring scale should
read 1-7/8 to 2 pounds just as the arm reaches its stop
screw. To overcome static friction, read the spring scale
while the arm is moving.
Scale Should Be Read Just As
Shift Arm Reaches Rest Position
Shift Arm Moves
Toward Left
FIGURE 51-B. Spring Scale Measurement For
Rotate Spring Adjustment
NOTE: The accuracy given to the next seven coarse
alignment adjustments determines the "band width" (de-
tenting variation) ofthe rotate system. Each one of these
seven ad justments contributes to the band width in a di f-
ferent manner. Generally, it takes experience in mak-
ingeachadjustmenttolearnhow much accuracy is need-
ed to end up with an accumulated band width which is
acceptable. The band width of the rotate system should
never exceed .030" nor should any extra time be spent
in trying to obtain one any less than .020".
Rotate Selector Latches
a. Form the stop lugs above the positive rotate selector
latches (Fig. 52) so that the latches will reset si-
multaneously (under the latch bai I) 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
o
\ I
ID~
- - - -------r-'\'
-
-----~
~---.l""""~
FIGURE 52. Rotate Selector Latches