Tally 424 Manual page 11

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Keep the star wheels and star wheel levers free of lint and hair. They must have
free movement to read tape without error. II lever movement becomes sticky, clean pivot bear-
ings with methyl ethyl ketone and relubricate with SAE 20 oil.
5.2.3 Read Head and Contact Adjustments (See Figure 13)
Reading errors may be caused by incorrect adjustment of the read head assembly.
The first step in adjustment is to verify that each of the eight star wheel levers
(36)
are free to
move in a vertical direction without drag on the adjacent levers .
The star wheels (37) must also be centered over the capstan . The star wheel
position with respect to the center of the capstan may be adjusted horizontally by loosening the ·
pivot bushing (30) and moving the read head adjusting eccentric (29). ·
The movable contact wires (34) must be free to move up and down in the gap be-
tween the fixed contacts (31). Improper alignment may be corrected by carefully bending the :
movable contact wire at its base.
The fixed contact gap opening must be between
.025
and
.030
inche.s wide . Exces-
sive gap may be corrected by bending the normally open (lower) contact.
Contact pressure should be 14-22 grams per pair of wires when in either the
N/O or N/C position. Lower contact (N/O) pressure may be checked by applying upward force
under the wires adjacent to the fixed contact, with a gram gage and wire tool as shown in Figure
14a. Observe the force required to lift the wires when switch contact is broken on the oscillo-
scope. Lower contact pressure is increased by moving the fixed contact block upward.
(a}
(b)
Figure 14. Checking Contact Pressure with a Gram Gage:
{a) checking lower contact pressure;
{b) checking upper contact pressure
SEATTLE
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