Keyboard Lock - IBM Selectric I/O Manual Of Instruction

Check Latch
FIGURE 53. Check Latch
Depending on the printer wiring either "odd" or "even" bit
check may
be
used.
Code check does not insure that the correct character has been
printed, only that the correct number of selector latches are
active.
Feedback Contacts (C 1-C2)
This contact assembly is located on the left hand side of the
printer. The purpose of C1 is to provide a gailng time for the
selection and checking contacts. The purposes of C2 are to
provide gating of the print magnet pulse and to electrically
prevent any other function from taking place during a print
operation.
KEYBOARD LOCK
On some machines when the ON/OFF switch is turned OFF,
the keyboard must be locked to prevent mechanisms from being
tripped whi Ie the motor is not running. This is to prevent the
motor from having to start under a load and to prevent an un-
wanted operation the next time the switch is turned ON.
Operation of the switch level controls the keyboard lock
mechanism by rotating the lockout bai I that extends across
the bottom of the keyboard section (Fig. 54A). When the
switch lever is in the OFF position, the lockout bai I is moved
Selector Compensator
Switch Lever
-~f'l"-;:
FIGURE 54A. Keyboard Lock Mechanism
- ON Position (Early)
20
forward contacting the pawl stop which is positioned below
an extension of the cycle clutch latch pawl, and prevents the
cycle clutch from being released.
As additional insurance against an interposer being latched
down, a special bellcrank at the left side of the keyboard is
rotated into the selector compensator by a I ink from the lock-
out bail. This forces the steel balls to shift in the tube and
block the downward movement of all interposers. When the
switch is ON, the keyboard lock bellcrank is spring-loaded out
of the selector compensator.
A link from the right side of the lockout bail rotatesaD-shaped
shaft beneath the operational mechanism. The shaft locks the
backspace, spacebar, carrier return and indexing keylevers
when the switch is OFF. The tab and shift keylevers are not
locked.
Keyboard Lock Solenoid
The keyboard lock solenoid is mounted to the bottom side of
the powerframe. The solenoid is held by a U-shaped bracket
that is bolted to the frame (Fig. 54B).
MOUNTING BRKT. SOLENOID BELLCRANK
FI GURE 54B. Keyboard Lock Mechanism
Lockout Lever
A bracket holds the lock-out lever in place. The bracket is
fastened to the top of the power frame and to the solenoi d
mounting bracket. The lock-out lever is fastened to the brack-
et by a shoulder pivot screw.
The lock-out lever is positioned front to rear. The front of
the lock-out lever contacts the keyboard lock bail roller. A
spring is fastened to the rear of the lever, pull ing it down.
This causes the front of the lever to move up anytime the sole-
noid is not energized.
The sloped surface of the lock -out lever contacts the bai I roll-
er. As the lever moves up or down, depending on which way
it is installed, the roller wi II be cammed forward. Figure 55