IBM Selectric - Page 71

caustdbj the fact that the effect of the drag spring felt
at the feed and pressure rollers increases as the amount of
ribbon onthesupplyspool diminishes. And, in addition,
the effect of the take-up spool tension felt at the feed
and pressure rollers decreases as the diameter of the used
ribbon on the take-up spool increases.
If the ribbon should become slack in the ribbon circuit
by improper operation of either the supply spool Lrake,
supply drag lever, or the supply spool drag spring an
overly sensitive ribbon tracking condition wi II exist.
2. Shock Spring - Position the shock spring so it is approxi-
mately .040"tothe right and parallel to the edge of the
ribbon feed plate (Fig. 200). The shock spring should be
formed at the front maki ng the roller on the spri ng lean
approximately lOe to the left.
3. Supply Drag Lever - The supply drag lever must contact
the outer wrap of ribbon on the supply spool at the center
orslightlyabove (Fig. 202). Form the lever up or down
to obtain this condition. Do not form it front to rear.
Supply Drag Lever
(Contacts Center of Ribbon)
FIGURE 202. Supply Drag Lever
NOTE: After forming the lever make sure that it does
not bind on its pivot screw.
CAUTION: If the supply drag lever contacts the ribbon
be low center, the outer wraps of ribbon on the spool wi II
tend to creep up which may cause ribbon spi Ilage.
4. Corner Guide - The corner guide is aligned parallel to
the feed roller at the factory and should not require ad-
justment unless damaged or replacement is necessary. If
an adjustment is required the corner guide should be
formed at the bottom so that it is vertical to the feed
plate and clears both flanges of the take-up spool (Fig.
203) .
5. Tracking Post - The tracking post is positioned and aligned
parallel tothe feed roller at the factory with gauges and
should not require adjustment unless damaged or replace-
ment is nece:-sary. If an adjustment is necessary the fol-
low:,!. e,bre sho'-.;\d be used:
70
a. Position the tracking post under its mounting screw
so that it clears the flanges of the transparent take-
up spool by approximately 1/32" (Fig. 203).
FIGURE 203. Corner Guide & Tracking Post
b. Form the tracking post at the bottom to achieve
verticalness with the feed plate:
The following technique may be used to check
verticalness: First, remove the typehead and then
hold the load bai I open just far enough to disengage
rhe pressure roller from the feed roller (Do not open
the load bai I so far that the supply drag lever is held
away from the spool of ribbon on the supply spool) .
Now, operate the repeat underscore and observe how
the ribbon tracks from the corner guide to the feed
roller. If the tracking post is verti ca I the ribbon wi II
be centered as it passes between the two flanges of
the transparent take-up spool (Fig. 204). It should
alsotrackonthecenterofthe feed roller and evenly
between the two flanges of the tracking post without
touching either flange.
Pressure Roller disengaged
from Feed Roller
FIGURE 204.
T racki ng Post
Corner Guide
Track Post Ferticalness