IBM Selectric Maintenance Manual page 47

Direction
.....
Adjustment Made
With Eccentric Stud
t-t----.010"
To
.020"
~
Notch In Type Head
. -.1
Detent
FIGURE 81. Final Typehead Homing
justed and the roller reseated until the 1/16" is ob-
tained. Having the roller seat 1/16" from the top
of the slot sets up a vertical condition between the
compensating arm and the rotate arm so that the lev-
erage within the arm assembly will be the same for
both positive and negative movements of the arm.
In some cases it may be found that after the eccen-
tri c stud is adj usted the roller wi II not drop but re-
main trapped at the top of the V-shaped slot. If
this occurs, lengthen the rotate link and then re-
check the eccentric stud adjustment.
NOTE: The eccentric stud should always be kept
in the lower half of its orbit so that it will tend to
turn in the tightening direction as it operates against
the sideframe. Also, if the correct detenting of the
-5 character cannot be easi Iy obtained with the ec-
centric stud adjustment the preliminary homing ad-
justment (Adj. #8) must be readjusted.
d. Damper spring stop - with the type head removed,
raise the stop so that when a lower case -5 char-
acter is half-cycled the damper spring will just col-
lapse against the sideframe. Check by pulling the
compensator arm away from the si deframe wi th n
spring hook and then allow it to go back in slowly
(Fig. 82).
Damper Spring Must
Be Completely Collapsed
FIGURE 82. Damper Spring Stop
2-24
The main purpose of the eccentric stud adjustment is to
stop the negative motion of the rotate arm as it approach-
es the negative five position so that all of the pressure
on the compensator roller wi II be relaxed when the com-
pensating arm has reached its full negative position.
Assuming that no ratio change was felt in the system at
the time of making the eccentric stud adjustment, stop-
ping the rotate arm early to relax the pressure on the
roller will cause the negative motion of the rotate arm
between the negative four and negative five rotate po-
sitions to be reduced, or the detenting of the negative
five to be positive with respect to all the other rotate
positions •
Since the ratio change adjustment will not affect the
negative five position, the typehead is then rehomed to
the negative five position making it detent properly but
causing all of the other positions (-4 through +5) to de-
tent too far negative. The lost motion of the rotate arm
is sti II fe It between the negative four and negative five
rotate positions. The rotate arm motion in this area can
be controlled by the ratio change adjustment which will
be discussed under the next adjustment. This rehoming
of the typehead to the negative five position (which is
usually a slight refinement of the original homing ad-
justment) is accomplished by the eccentric stud adjust-
ment rather than by slipping the rotate shaft within the
rotate pulley. It has been found that the homing adjust-
ment can readi Iy be refi ned to the negative five position
with the eccentric stud while at the same time obtaining
a relaxed condition for the compensator roller (accom-
plished by controlling the length of the rotate link and
reseating the compensator roller).
12.
Ratio Change Adjustment - With the machine half-
cyc led to an upper case -3 character, form the pad-
d Ie on the rotate eccentri c arm unti I the upper case -3
character detents the same as the upper case -5 character.
Each time the paddle (Fig. 83) is formed the machine mustl
be recycled under power before observing the detenting of
FIGURE 83. Arm Assembly In -3 POsition