IBM Selectric Manual

8.
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 rotute arm vel-tical at a half-cycled zero rotate
position, the leverage within the rotate arm wi II be the
same for positive and negative movements of the arm.
The adjustment can be measured using the #1 scribe line
on the Hooverometer handle as illustrated in Figure 55.
The scribe I ine measurement makes allowance for the
thickness of the compensator damper spring.
It is important that this adjustment be set as carefully as
poss i
bl e and ma i nta i ned, be cause subsequent ad j ustments
are dependent upon the correct starting point of the ro-
tate arm.
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.
Preliminary Typehead Homing - Half-cycle the machine
under power using the upper case letter IITII. Loosen the
set screw in the bottom of the rotate pulley and sl ip the
type head so that the detent wi II enter .010
11
to .020"
from the centerofthe detent notch, on the negative side
of the notch, when the head play is lightly removed in
the negative direction (Fig. 56).
FIGURE 56. Type Head Homing
The main purpose of this preliminary homing adjustment
istoaid the Customer Engineer in making the rest of the
coarse alignment adjustments. It places the typehead
in approximately the correct position so thut its rotation,
for a given selection, may be easily measured and used
as a
tool in making the next four adjustments. After com-
pletingthissequenceofadjustmentsthe preliminary hom-
ing adjustment may have to be refined.
NOTE: Be sure to maintain .002" to .004" end play in
the rotate shaft when makingthisadjustment. Also, make
sure
that the compensator roller is 1/16" from the top of
the slot.
9. Balance Lever - With the machine in upper case loosen
the lock nut on the balance leverand move the right hand
memberof the balance lever (Fig. 57) left or right until
a
half-cycled +5/-5 combination detents (coarse aligns)
the same as a half-cycled letter "Til. The combination
can easily be obtained by holding the negative-5 latch
interposerforward with the fore finger whi Ie striking the
letter "B" with the thumb (a letter "T" will result).
20
Ba lance Lever -----:~~/~r= ........ '"'""'lI-...:-
FIGURE 57. Balance Lever Adjustment
Begin the adjustment by half-cycling the letter "T" in
the normal manner. Check the detent entry to see exact-
ly how much off-center the detent enters with the head
play removed clockwise. Next hal f-cycle the letter "T"
using the cance Ilation method described above and check
the detent entry. If it is di fferent from the normal liT II ,
it indi cates that the type head has moved because of an
unbalanced condition between the positive and negative
motions.
With the machine in the half-cycled position using the
cancellation method, adjust the right hand member of
the balance lever left or right unti I the detenting is exact-
ly as it is when the letter "T" is half-cycled normally.
Changing the balance lever adjustment will not appre-
ciablyaffectthedetentingof the half-cycled letter "T".
NOTE: The nut on the balance lever screw can be left
loose unti I the correct adjustment is obtained. Be sure
not to move the adjustment when tightening the nut.
In Figure 58 the effects of the wear compensator are dis-
regarded and all adjustments are correct except the bal-
ance lever. The right hand member of the balance lever
ismaladjustedtoo fartothe left creating too much nega-
tive motion and not enough positive motion. Looking at
the positive side of Figure 58 you can see that the mal-
adjusted balance levercausesa progressive loss of motion
to the rotate bellcrank from the zero to a positive five
rotate position. The greatest loss of motion is felt at the
positive five position because the left end of the balance
lever receives the most motion for this selection. When
the negative side of the balance lever is operated, the

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