IBM Selectric - Page 54

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Machines locked in upper case can sometimes be adjust-
ed by the stud in the sh i ft arm.
Balance Lever - With the machine in upper case loosen
the lock nut on the balance lever and move the right hand
member
of the balance lever (Fig. 120) left or right un-
til a half-cycled +5/-5 (I/O Home) combination de-
tents (coarse aligns) the same as a half-cycled zero ro-
tate character. The combination can easi Iy be obtain-
ed by holding the negative-5 latch interposer forward
with the fore finger while striking a +5 character with
the thumb.
Balance Lever
o
FI GURE 120. Balance Lever Adjustment
Begin
the adjustment by half-cycling a zero rotate char-
acter in the normal manner. Check the detent entry to
see exactly how much off-center the detent enters with
the head play removed clockwise. Next hal f-cycle
using the cancellation method described above and
check the detent entry. If it is different from the nor-
mal zero rotate character, it indicates that the type-
head has moved because of an unbalanced condition be-
tween 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 until the detenting is exact-
ly as it is when a zero rotate character is half-cycled
normally. Changing the balance lever adjustment wi II
II Til
+5
+4
+3
+2
+1
0
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I/O Home (+5/-5)
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not appreciably affect the detenting of the hal f-cycled
zero rotate character.
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 Fig. 121 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
ismaladjustedtoofartothe left creating too much nega-
tive motion and not enough positive motion. Looking at
the positive side of Fig. 121 you can see that the mal-
adjusted balance lever causes a progressive loss of motion
to
the rotate bell crank from the zero to a positive five
rotate position. The greatest loss of motion is felt atthe
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
maladjusted balance lever causes the rotate bellcrank to
receive an excessive amount of motion as illustrated by
the detenting of the negative five rotate position. This
excessive motion is felt equally in all of the negative
selections because the negative end of the balance lever
receives the same motion from the cam for all negative
selections. The progressive loss of motion felt from the
negative five to the negative one rotate position is caused
by the positive side of the balance lever. It produces a
deficiencyofmotion in the negative selections just as it
did during the positive selections.
Notice the detenting of a negative one selection in Fig-
ure 121. This selection combines the error of a positive
four
and a negative five causing the negative one to be
the worst detenting selection with respect to the zero
rotate selection. Although the cancellation method
(+5/-5) combines even a greater error than the negative
one selection, either one may be used to effectively make
the balance lever adjustment. Checking the detenting
of the other positions is not necessary.
If the balance leverwereoutofadjustment in the opposite
direction so that there was too much positive and not
enough negative motion, the error pattern would remain
the same except that the detents would move towards the
opposite side of the detent notches.
"0"
-1
-2
-3
-4
-5
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FIGURE 121. Excessive Negative Balance
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