IBM Selectric Reference Manual

2.
If the bearing did not extend beyond the cam, the shift
clutch arbor could rub against the cam and create a noise
as well as a
drag on the cam when the cam was stationary.
Two problems could be created by having too much of the
bearing extending beyond the cam. A gap would exist
between the cam and the shift clutch arbor. This could
allow 01 coil of the shift clutch spring to wedge into the
gap and lock the machine. If the back-up roller were
excessively far to the left, the cam would be forced to
the left at the rear causing it to cock and bind at the
pivot.
The set screw for the back-up roller eccentric is acces-
sible through a hole in the cam with the cam in the lower
case position. The shift clutch mechanism including the
arbor should be removed in order to best observe the ad-
justment. Be sure that .002" to .004" end play exists in
the operational shaft when the arbor is replaced.
CAUTION: Any change in the position of the back-up
roller directly affects the typehead homing and the shift
arm motion
adjustments. Be sure to recheck these adjust-
ments.
Shift Clutch Spring Retaining Plate .0 Adjust the retaining
plate attached to the shift cam (Fig. 66) to satisfy the
following condition. With the machine turned OFF and
the shift cam detented, the shift clutch ratchet should
Clutch Spring
Re'taining Plate
FIGURE 66. Shift Clutch Spring Retaining Plate
rotate .028" - .059" when the shift release arm releases
the ratchet. The rotation can be observed relative to
the shift interlock (Fig. 67). Half the distance from
the center of one ratchet tooth to the next is 3/64" or
.047",
The adjustment ofthe retaining plate determines how much
the clutch spring will be expanded when the shift mech-
anism is at rest. Expanding the spring too much may
cause fai I ure of the cam to reach the detented position,
because the spring would be expanded too soon. Insuf-
ficient expansion would allow the cl utch spring to drag
when at rest creating a load on the motor and on the shift
release mechanism.
NOTE: If sufficient adjustment cannot be obtained with
the retaining plate, the right end of the clutch spring
may be
placed in another hole in the ratchet. The ad-
justment can then be refined with the plate.
2-17
A. REST POSITION
B. RELEASED POSITION
FIGURE 67. Shift Clutch Spring Retaining Plate Adjustment
2.1
Shift Clutch Ratchet Adjustment (Late) (Fig. 67. 1) -
Adjust the shift clutch ratchet to satisfy the following
condition. With the machine turned off and the shift
cam detented, the shift clutch ratchet will rotate .028"
to .050"when the shift release arm releases the ratchet.
The rotation can be observed relative to the shift re-
I ease arm a nd the sh i ft cam stop. Be sure to loosen the
set screw in the ratchet before adjusting. Note: Re-
move play from the shift ratchet in a clockwise direc-
tion before checking this adjustment.
Ratchet
FIGURE 67.1 Shift Clutch Ratchet Adjustment

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