IBM Selectric - Page 67

NOTE: Thisadjustmentpermitsthebrake to engoge the
ratchet teeth of the supply spool as lote as possible during
a ribbon feed operotion. If the brake is allowed to en-
goge the supply spool too early the amount of tension in
the ribbon circuit wi II become inconsistent from one feed
operation tothe next. That is, as the brake is permitted
to engage the supply spool too early during each ribbon
feed operation, the ribbon becomes tighter and tighter in
the ribbon circuit unti I finally the excessive tension cau-
ses a spooli rg off effect to the suppl y spool. The ribbon
then remains siack in the ribbon circuit for ~everu: feeJ
operations unti I the brake can bui Id up the tension again.
This inconsistent tension in the ribbon circuit wi II con-
tribute or may even create a poor ribbon tracking char-
acteristic at the feed and pressure rollers. Also, char-
acter overlap on the ribbon may be present each time the
ribbon becomes slack.
Insufficient engagement of the brake with the supply
spool wi 1\ allow the ribbon to become slack in the ribbon
circuit (especially durin9 a repeat spacebar or backspace
operation when the carrier is under excessive vibrations).
This wi 1\ also lead to Sensitive tracking and intermittent
overlappi ng characters an the ribbon.
CAUTION: Be sure that the stenci I lever is not in the
stenci I position when making this adjustment; otherwise,
an erroneous adjustment may resu It.
SERVICE HINT: Toforrnthe lug on the brake actuating
lever place a screwdriver as shown in Figure 195 and then
slowly twist the fbt porti on of the lug with duckbill
pliers. Do not attempt to form the curved porti on of the
lug as itis brittle and breaks easi Iy.
The purpose of the screwdriver as shown in Figure 195 is
to eliminate any pressure that might be placed on the
vertical lug of the lift guide plate whi Ie making this
forming adjustment.
Brake Actuating
Lever
I
FIGURE 195. Forming Technique
66
RIBBON LIFT
1. Lift Guide Plate - With the ribbon lift cam follower on
the low point of the lift cam, position the lift guide
plate on the arm of the lift guide assembly to satisfy two
conditions (Fig. 196).
a. Position the lift guide plate vertically so that the
rearofthe lift guide assembly rests 1/32" above the
carrier cas.ting when the stenci I lever is not in the
... ___ :1 _~,: .. :~~ {r:::~ 10,t.\
"1 t;;;;;II\".o1 I t"'VJII I \",III ,I 1::;1. I' ..... '.
b. Position the lift guide plate so that its bottom sur-
face (where the control link operates) is parallel to
the slot in the cam follower.
Lift Guide
o .... j
'·'=0-=-'=:=-.": -----r-
,~., >:. ,
'. • I
. .
. ', ... " 1/32"
Clearance
lift Guide Plate Cam Follower
FIGURE 196. Ribbon Lift Guide Plate
Adiusting the plate up or down so that the lift guide as-
sembly is resting 1/32" above the carrier insures that
there will be no lost motion from the ribbon lift cam
through to the lift guide assembly. Keeping the bottom
surface of the lift guide plate parallel to the slot in the
cam follower insures that the lift guide assembly will re-
ceive the proper amount of lift motion for each one of
the four different lift positions.
SERVICE HINT: The vertical position of the lift guide
platemaybecheckedbyobserving the liftguideassembly
while manually pushing the control link all the way to
the rear into its stencil position. The guide assembly
should drop 1/32" at the rear if the adjustment is cor-
rect .
Parallelness of the lift guide plate with the slot in the
cam follower may be checked in the following manner:
With the cam follower resting on the low point of the
lift cam, disconnect the control link and manually slide
the link back and forth through the four lift positions
(Do not slide the link into the stencil position). If the
plate is parallel, no movement will be produced to the
ribbon lift guide assembly whi Ie sliding the link back and'
forth.
Figure 197 illustrates how a maladjusted lift guide plate
will affect each one of the four ribbon lift positions. A
series of His are used for simplicity to show the position
of the typed characters on the fi 1m ribbon.