IBM Selectric Reference Manual

SECOND INSPECTION PERIOD
SELECTION
MAGNET UNITS
1. Check the pick times of all magnets by observing (on an
oscilloscope) the voltage rise across a 10-ohm, 1/2-watt
resistor (part 321271) in series with the individual magnet
coils, when a 48-volt pulse is applied to the coil. All
pick times must be ten milliseconds or less, with the ex-
ception of U.C 0 shift magnet, red ribbon shift magnet and
the keyboard-lock solenoid. The U.C. magnet and red
ribbon shift magnet armatures must seal within 12 milli-
seconds maximum and the keyboard lock solenoid must
pick in a maximum of 55 milliseconds. See Figure 14for
wave form of magnet pick time.
.1 PICK or SEAL I-
-j TIME
Figure 14. Waveform 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 rocki ng 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.
OPERATIONAL MAGNET UNITS
1. When an armature is operated, the armature pull-link ad-
justment should allow for positive interposer tripping with
.002" - .010" 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 clearances.
Clean all operational circuit-breaker contacts, and check
for pitting.
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 mec;,hanism). On the
spring-loaded (new style) trip mechanism, overthrow(with
an armature operated) should measure .005" - .020" be-
tween the trip lever and the latch lever. Check to insure
thar the K. O. eccentri cs do not choke off the armature
travel (K.O. eccentrics should clear trip bail extensions
by .003" to .008" with armatures manually attracted).
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 bai I 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.
1-12
CYC LE C LUTC H
1. Latch height: Measure with #3·scribe line on Hoover-
ometer.
2. Cycle shaft collar: The cycle clutch should begin toslip
approximately 15
0
before the check pawl detents. Hand
cycle the machine, using a -5 rotate, O-tilt character.
3. Nylon stop: Adjust for four degrees rotation or overthrow
when the cycle shaft is latched home.
4. Shaft end play: .001" - .003".
5. All gears: Minimum play, no binds, screws tight.
6. Print-shaft timing: The keyway should be toward the
dowel pin on the carrier.
7. Filter-shaft timing: With an interposer latched down,
there should be .005" - .010" between the interposer
and the fi I ter shaft.
THIRD INSPECTION PERIOD
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 between the con-
tact-strap stop and the latch (interposers unlatched).
2. There should be .002" - .010" clearance between the print-
feedback O/Pls 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 remain
transferred during tabulation and must transfer before the
backspace cam reaches its high point.
4. The carrier-return-interlock (normally-open) strap should
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
~r similar tools be used to clean gold contacts in this
machine.
To clean the gold contacts, use IBM Contact Cleaner and clean
bond paper.
RIBBON FEED MECHANISM
1. A -5 rotate, I-tilt character should strike the ribbon 1/16"
from the bottom in the high lift position.
2. Check for enough tension of the ribbon-feed mechanism-
ratchet-brake springs to hold the ribbon ratchets in a ro-
tated position, to overcome positively the action of the
centering spring.
3. The ribbon-feed pawl should hold the reversing interposer
within .005" - .010" of its total travel with the ribbon-
feed cam on its high point and the ribbon mechanism set
for a reversing operation. Positive two-tooth feed plus
.010" overthrow should result.

IBM Selectric Specifications

General

Type	Electric typewriter
Introduced	1961
Keyboard Layout	QWERTY
Carriage Return	Electric
Manufacturer	IBM
Printing Technology	Typeball (golf ball)
Power Source	AC Power
Power Supply	120V AC