IBM Selectric Manual page 27

J
3. Pri nt Shaft Ti m i ng - Advance or retard the pri nt shaft
relative to its gear to obtain the proper timing of the
rotate detent. Because of a sl ight redesign of the detent
cam on machines equipped with an impression control
lever, the specifications of the timing adjustment for
these machines is slightly different than the adjustment
required for machines that are not equipped with an im-
pression control lever. Be sure to use the correct ad-
justment:
a. Machines Equipped With An Impression Control
Lever - Whi Ie slowly hand-cycl ing an upper case
"M" (-5) remove the head play lightly in the posi-
tive direction (against the direction of rotation) and
observe how the rotate detent ENTE RS the detent
notch. It should clear the side of the detent notch
by .001" to .015" just as it enters (Fig. 68a). This
entry clearance should cause the detent to scrub on
the sideofthe detent notch during withdrawal when
the machine is hand-cycled back to rest. During a
powered operation the dynam i cs of the system causes
the typehead to lag behind by as much as 12° during
the restoring portion of the cycle, therefore this
scrubbing on withdrawal is not felt in the system
when the machine is operated under power.
"ENTRY"
IWITHDRAWAL"
FIGURE 68a. Detent Timing OJ The "M"
Adjusting the detent timing so that the detent scrubs
lightly on withdrawal when the machine is hand-
cycled insures that the detent withdrawal wi II not
begin to occur before the typehead prints.
NOTE: Check the detent entry for an upper case
"W ". The detent must enter the correct detent
notch.
CAUTION: After hand-cycling the machine the
compensator roller must be raised to the top of the
wedging slot and reseated under power by striking
a series of "Mls".
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b. Machines Not Equipped With An Impression Control
Lever - Hand-cycle an upper case "M" (-5) and
observe the rotate detent as it operates in the type.-
head notch. The detent must enter the correct de-
tent notch and withdraw without restricting the re-
storing of the typehead. There should be .002" to
.004" backlash felt in the type head when the detent
has withdrawn approximately half-way down the
slope of the detent notch (Fi g. 68b).
Afteradjustingthetimingof the rotate detent to the
upper case letter "M" (-5), check the detent entry
and withdrawal of an upper case letter "W
II
(+5).
I fthe detent restri cts the type head from restori ng on
withdrawal when the "W" is slowly hand-cycled,
advance the print shaft slightly until the "W" has a
withdrawal backlash of .002" to .004". When the
withdrawal adjustment has been completed check
the detent entry on bath the "W" and
II
Mil . The
detent must enter the correct notch.
CAUTION: After hand-cycling the machine the
compensator roller must be raised to the top of the
wedging slot and reseated under power by striking
a series of "Mls".
Typehead Restoring
~
FIG URE 68b. Withdrawal Clearance
For The "M"
(-5)
If
difficulty is encountered in obtaining the correct detent tim-
ing, check the following items:
a. Detent skirt clearance - favor the high side of the
tolerance.
b. Typehead homing - favor the high side of the tol-
erance.
c. Band width - make sure that it is not excessive.
d. Head play - it should be .048" to .067" measured
at the typehead skirt. If excessive head play is
suspected the ball joint should be replaced and the
typehead homing adjustment refined.