Third Inspection Period - IBM Selectric Maintenance Manual

Note: Check as follows. Half-cycle the character and
remove detent from the head. Take the play out of th-e
head in a clockwise direction. Allow the detent to re-
turn slowly, and observe the point the detent strikes or
enters the skirt. Bandwidth equals the difference between
the best and worst character.
DETENTING
I
1.
\
2.
Print-shaft timing: The detent must enter and leave the
head without hitting the skirt. Check by manually hal f-
cycling. Use a -5, home, and a +5 character.
The skirt clearance should be .025" - .035" in a 2-tilt
position. When both dp.tents are engaged fully in their
respective notches, there should be .001" minimum mo-
tion of the detent-cam follower with respect to the detent
lever.
THIRD INSPECTION PERIOD
)
SELECTION MAGNET UNITS -- SCOPE PROCEDURE
,\. Check the pick times of all magnets by observing (on an
osci lIoscope) the voltage rise across a 1 O-ohm, 1/2 watt
resistor (part 321271) in series with the individual magnet
coi Is, when a 48-volt pulse is appl ied to the coi \. All
pick times must be ten milliseconds Qr less, with the ex-
ception of U.C. shift magnet, red ribbon shift magnet
and the keyboard-lock solenoid. The U.C. shift magnet
and red ribbon shift magnet armatures must seal within 12
milliseconds maximum and the keyboard lock solenoid
must pick in a maximum of 55 milliseconds. See Figure
13 for wave form of magnet pick time.
Pick-time readings are the best indicator of magnet per-
formance. High pick times foretell adjustment discrepan-
cies, wear, or sluggishness. They are often evidenced
by noticeable machine slowness when repeat operations
are performed. Note the following items when high pick
times are encountered:
a. With the armature manually attracted, an armature-
to-yoke clearance of • 001" - • 006" is necessary to
prevent an armature from rocking on the yoke. Care-
fully check the pivot points for Wear (pivot plate ad-
justment) •
b. Except in the case of the operational magnets, the
armature stops are to be adjusted for a .004" - • 008"
armature-to-yoke clearance. This clearance must be
maintained to prevent permanent residual effects in
the armature.
c. In no case should an armature rock on the core.
I
PICK or SEAL
I-
~
TIME
FIGURE 13. Waveform of Magnet Pick Time
1-11
CYCLE CLUTCH UNLATCHING
1. Positive unlatching of the cycle clutch must occur when
each armature is operated by hand, with the latch over-
throw .002" - .007" (old style trip mechanism). On the
spring-loaded (new style) trip mechanism, overthrow
(with an armature operated) should measure .005" - .020"
between the trip lever and the latch lever. Check to in-
sure that the K.O. eccentrics do not choke off the arma-
ture travel (K.O. eccentrics should clear trip bail exten-
sions by • 003" - • 008" with armatures manually attrocted).
2. Check for .005" - .010" vertical clearance between the
selection-armature latching surface and the pushers, and
for .001" - .010" horizontal between the tip of the push-
ers and the armatures.
3. The trip bail pivot eccentrics must allow equal motion to
be transmitted from the T2 and R5 armatures to the trip
link. The eccentrics must be in the upper sphere of their
adjustment to prevent binding.
OPERATIONAL MAGNET UNITS
1. When an armature is operated, the armature pull-link ad-
justment should allow for positive interposer tripping with
. 002" - • 01
A"
overthrow clearance between the interposer
and the pawl guide plate at the point of unlatching.
PUSHER UNIT
1. Both latch-pusher cam-follower rollers must contact the
cams on the selector cam shaft throughout a cycle.
2. Check the individual pusher-to-Iatch extension clear-
ances. Clean all operaHonal circuit-breaker contacts,
and check for pitting.
CONTACTS
1. The operational transmitting contact latches should be
flush with the end of the contact-strap stop (interposers
latched), and should have .005" - .015" clearance be-
tween the contact-strap stop and the latch (interposers
unlatched) •
2. There shou Id be .002" - • 010" clearance between the
print-feedback O/S's and the low point of the feedback
cams.
3. The tab interlock microswitch should move at least .031"
after the switch has transferred when the tab torque bar
is moving toward its rest position. The switch must re-
main transferred during tabulation and must transfer before
the backspace cam reaches its high point.
4. The carrier-return-interlock (normally-open) strapshould
rise a minimum of .010" off its support terminal with the
carrier-return-clutch latch latched.
5. Check the timing and air-gap adjustments on all contacts.
All transmitting and checking contacts should have:
a. .020" air gap except the shift which is .040".
b. All circuit-breaker contacts and interlocks should
have a .040" air gap.
CONTACT CLEANING
Caution: Under no condition should contact files, burnishing
blades or similar tools be used to clean contacts in this machine.
To clean the contacts, use IBM Contact Cleaner and clean bond
paper.