IBM Selectric Manual

ADJUSTMENT THEORY
MOTOR AND DRIVE
1.
2.
3.
4.
Drive Belt - Adjust the .motor mounting brackets forward
or back to obtain a minimum amount of belt noise.
Bothendsofthemotor must be adjusted the same in order
to maintain the rotor shaft perpendicularto the drive belt.
The belt must never be so loose that jumping cogs on the
motor pulley is a possibi I ity. Check by operating the
shift mechanism whi Ie holding the carrier with the carrier
return in operation. This loads the motor to a point where
failure will be most probable.
Motor Pulley - Adjust the motor pulley left or right so
that the drive belt ridesfully on the teeth of both pulleys
without rubbing the flange of either.
Motor Clutch Pawl Stops (Fig. 1) - Form fora clearance
of .0101lto .020
11
between the clutch pawl tip and pulley
ratchet when the pulley is manually rotated.
Form This Tip
FIGURE 1. Motor Clutch Pawls
Idler Gears - Adjust the idlergear studs so that minimum
backlash is present between mating gears. The mechanism
must be free of binds throughout 360
0
rotation ofthe gears.
Minimum backlash is necessary to prevent erratic opera-
tion of the drive train and to insure minimum overthrow
of the driven shafts.
The lower idler gear must be adjusted first because the
upper idler gear is adjusted to the final position of the
lower gear.
CAUTION: After any removal and replacement of the
left hand cycle shaft bearing, the mesh of the lower idler
gear must be checked. The loweridlergearstudis mount-
ed to the bearing plate; therefore any sl ight rotation of
the plate will affect the gear mesh.
KEYBOARD SECTION
1 . Fi Iter Shaft - With the cycle shaft in the rest position,
the working surface of the filter shaft should clear a de-
pressed interposer by .005
11
to .015
11
(Fig. 2).
2.
1
Adjust by rotating the fi Iter shaft to the correct position
after loosening the fi Iter shaft gear.
--~ .. -- .010" to .015"
Fi Iter Shaft ~)
All Backlash Removed
In This Direction
FIGURE 2. Filter Shaft Adjustment
All backlash ofthe gear train should be taken out forward
when checking the fi Iter shaft adjustment. This simulates
a powered operation in which the momentum rotates the
top of the fi Iter shaft to its extreme forward position.
Insufficient clearance between the fi Iter shaft and the
interposers could allow the fi Iter shaft to stop just under
the rearof the interposers. The keyboard would then be
inoperative, because the interposers could not be de-
pressed.
Excessive clearance would delay the operation of the
interposers. The selector latches would not be pulled
forward unti I after having been pulled down sl ightly by
the latch bai I. This would result in excessive wear and
a noisy operation as the latches were snapped forward
from under the bai I.
CAUTION: Excessive clearance will also cause mal-
selection.
NOTE: Be sure to maintain .00211 to .004
11
end play of
the filter shaft within the left hand filter shaft bearing.
The mounting of the left hand fi Iter shaft bearing allows
.011
11
lateral play of the bearing. Do not confuse this
lateral play ofthe bearing with the fi Iter shaft end play.
Rear Interposer Guide Comb -Adjust the interposer guide
comb up or down so there is .020" to .030" clearance
between the bottom edge of the interposers and a vane
of the fi Iter shaft (F i g. 3).
The four interposer guide screws are accessible by insert-
ing the medium screwdriver between the letter keylevers,
beneath the front row of keybuttons.
CAUTION: Check the clearance at several points along
the fi Iter shaft.
NOTE: The purpose of this adjustment is to prevent
IIbridging". "Bridging" is a form "f malselection caused
by two or more interposers being depressed in front of
the filter shaft and driven forward at the same time.
Proper adjustment of the rear interposer guide comb al-

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