IBM Selectric Manual

velocity control plate eccentric until a slight drag
is felt on three tab cards inserted between the type-
headandthe platen(Fig. 76). A heavy drag should
be felt on four cords. No drag should be felt on
two cards. You should not be able to insert five
cords,
This will place the limit of powered travel of the
f !,~le fl,?f1,-j O?O" to .030" away from the platen
(providing the typehead with the proper amount of
tree flight),
Hand-cycle the machine unti I the print com follower
is at the low point of the cam. This may not be at
t~e rest position. The low point of the cam can be
0
c
?termined by observing the movement of the head
r:)'·,ard the front of the machine. With the typehead
01 its most forward point, adjust the velocity control
pI]te pin forward or back in the cam follower slot
until a clearance of .260" to .270" exists between
the center of the letter "Z" and the platen (Fig. 77).
Since this. 260" to .270" is measured between the
typehead and the platen it is not a measurement of
the powered travel of the typehead. The .020" to
.030" free flight is included in this .260" to .270"
and must be subtracted in order to determine the
amount of powered travel. The powered travel must
never exceed .265" as this wi II cause typehead
breakage.
The base of the Hooverometer handle can be used
asa measuring device as illustrated in Fig. 77. The
handle base is about .250" thick; however they do
not all measure the sarne. Each handle should be
measured with a dial indicator or micrometer to
determine its exact size. When the size of the
handle base is determined, a thickness of tab cards
should be placed around the platen that will total
.260" to .270" when added to the thickness of the
handle base.
FIGURE 77. Velocity Control Plate Adjustment
30
7.
e, Both adjustments must be rechecked and refined until
these conditions are obtained. Be sure to tighten
both screws firmly when the adjustments are com-
pleted,
NOTE: The ad justments shou ld be checked with
the ribbon removed,
These (di'_'~tmpntc; nre designed to produce optimum
print quality for most applications; however, a cer-
tain amount of variation in velocity is permissible in
order to satisfy a customer1s appl i cat ion. Be cautious
of creating an excessive increase or reduction in
velocityas this will adversely affect the uniformity
of impression between characters and the generai
appearance of the printed copy.
Anvil - The eccentric at each end of the anvil is ad-
justed so that the anvi I properly restricts the free flight
of the typehead. The adjustment can be checked by
typing a period with the copy control lever set all the
way back. The period should fai I to print or print very
faintly. With the copy control lever pulled forward one
notch (fourth position), the period should print lightly.
The ribbon and one sheet of paper should be used when
making the check. The check should be made at each
end ofthe platen only, because flexing of the parts wi II
allow a slightly different condition in the middle of the
platen. The high part of each eccentric should be kept
to the rear.
NOTE: The restoring cam follower eccentric should be
adjustedallthewayup while the anvil is being set. On
723
1
s
and 725
1
s
the carrier buffers must also be moved up
out of the way of the anvi I (Fig. 78).
The free flight must be restricted to insure that the char-
acters will all emboss the paper to the same depth. If
no restriction were applied, the smaller characters such
as punctuation marks would be allowed to emboss too
deeply. The surface area somewhat restricts the amount
of embossi ng for the larger characters; thus if the free
flight of the rocker is stopped at the right point I even
impression between all characters wi II result.
CAUTION: Raising or lowering either end of the anvil
will slightly affect the adjustment at the other end. Be
sure to recheck each ad justment. A clearance of .010"
to .045" must be maintained between the left anvi I
bracket and the sideframe for noise reduction purposes.
Adjust the bracket left or right on the anvil to obtain
the clearance (721 only)
8. Carrier Buffers (723 and 725 only) - A buffer plate at-
tached to the right side of the carrier and an adjusting
screw under the left side strike the top of the anvil to
prevent the print shaft from flexing downward. Each
should have .002" to .004" clearance with the top of
the anvil (Fig. 78).

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