IBM Selectric - Page 72

6.
If the ribbon is not centered on the feed roller or
tends to drift steadi Iy in one direction (either up or
down) on
the feed roller or tracking post, the track-
i ng post is out of verti ca I and must be formed front
or
rear to correct this condition. Forming the post
top toward the rear wi II cause the ribbon todrift up;
toward the front causes the ribbon to drift down.
The flanges on the tracki ng post wi II not stop or a Iter
drifting of the ribbon if a definite ribbon drift con-
dition exists. The function of the flanges is only to
confine the slight up and down drift of the ribbon
which is inherent in the mechanism (caused by the
feed and pressure rollers reaction to the varying
vertical position of the embossed characters on the
ribbon) .
c. Loosen the set screw in the flanged porti on of the
tracking post and adjust it up or down so it just spans
the ribbon (Fig. 204). Check the adj ustment by
observing how the ribbon tracks between the flanges
when operating the repeat underscore whi Ie holding
the pressure roller disengaged from the feed roller.
NOTE: Adjustments lib" and "c" must be consid-
ered together.
Pressure Roller - Adjust the pressure roller up or down by
its mounting stud so that it engages the center of the
crown on the feed roller as shown in Figure 205.
(Adj. Stud)
Feed Roller
Lock Nut
FIGURE 205. Pressure Roller Adjustment
The adjustment of the pressure roller may be checked by
observi ng how the ribbon tracks between the flanges of the
tracking post whi Ie under a typing operation. Since the
position, size, and shape of the embossed characters on
the ribbon have a definite effect on the ribbon tracking
at the feed and pressure rollers, the followi ng procedure
shou Id be used to check the pressure roller adjustment:
Type a series of upper case straight line characters (such
as
His, I's, Lis, and 1's) and observe how the ribbon
tracks between the flanges of the tracking post as these
characters embossed on the ribbon are passing between
the feed and pressure rollers. If the pr~oller ad-
justment is correct these upper case characters wi II cause
the ribbon to slowly drift up against the upper flange of
the tracking post without curling or climbing over. Now,
type a repeat underscore and observe how the ribbon
tracks between the flanges of the tracking post as the
embossed "underscores" are passing between the feed and
71
pressure rollers. If the pressure roller adjustment is cor-
rect the ribbon wi II slowly drift down against the lower
flange without curling or climbing over. If the ribbon
has a definite tendency to drift either up or down, re-
gard less of what characters are typed, the pressure rol-
ler must be adjusted in the direction of the drift to cor-
rect for the dri ft.
Since the pressure roller adjustment has good response,
it is suggested that the mounting screw be turned only 1/4
of at urn at a time when correcting for drift. Also, after
each adjustment it is necessary to re-tighten the lock nut
before observing the tracking.
CAUTION: Be sure that the small stabilizing pin riv-
eted to the under side of the pressure roller lever is always
in contact with the top surface of the feed plate (Fig.
206). If the stabilizing pin fails to stay in contact with
the feed plate, the engaged position of the pressure rol-
lerwillvaryverticallyeach time the load bail is opened
and closed. This wi II cause extreme difficulty in ob-
taining and holding the correct pressure roller adjust-
ment.
NOTE: The pressure roller mounting stud should be
approximately parallel tothe previously aligned tracking
post. Check by partia Ily disengaging the pressure roller
from the feed roller and sighting past the tracking post
as shown in
Figure 206. If the mounting stud is notice-
ably out of parallel the pressure roller lever should be
twisted carefu Ily with duckbi II pliers at the point shown
in Figure
206. After forming make sure that the stabi 1-
izing pin is sti II resting against the top surface of the
feed plate.
Pressure Roller
Lever
Pressure Roller
Mtg. Stud
(Stabilizing Pin)
Tracking
Post
FIGURE 206. Pressure Roller Mtg. Stud Alignment