IBM Selectric Maintenance Manual page 110

1.5
1.6
1.7
1.8
Adjust the intermediate lever, front to rear, so that
the escapement paw I does not fa II into the next rack
tooth when hand cycling. The escapement pawl
should ride to a point just before it drops into the rack
tooth.
Binds - Check the following:
a. Feed roll mounting arm hits the tab overthrow
stop.
b. Dust covers and card holders.
c. Anvi I and front carrier shoes.
d. Rear carrier shoe.
e. Escapement cord is off its pu Iley .
f.
Pinion Gear.
Adjust Tab Lever stop on the escapement paw I mount-
ing bracket so that both pawls bottQm fully in the
rack and the extensi on lug on the tab lever clears the
pawls by .001" - .003".
Backspace may go a fu II space but a worn escapement
paw I wi II cause the carri er to ski p ahead 1/2 space.
See Fig. 3.1. Look for this condition under powered
operation. To prevent a reoccurrence, replace the
escapement pawl AND rack.
1.9 S.H. OPERATIONAL CAMS
Effective with SELECTRIC I/O Printer SIN 4609595,
a new operational cam and ratchet wi·11 be in pro-
ducti on. The cam ratchet has been extended and the
bearing surface within the cam has been elongated to
provide longer bearing life. The cam wheel mounting
stud has a Iso been extended so as to provi de greater
release lever bite on the cam wheel. The improved
bite wi II eliminate extra cycles of the Operational
cams caused by the release lever slipping off the
si de of the clutch whee I .
Part No.
1159886
1159267
1159269
Description
CR cam
SB cam
Ratchet
1.10 S.H. OPERATIONAL INTERPOSER RESTORE BAIL
When the operati ona I interposer restore bai I requi res
readjustment to insure positive overthrow of the in-
terposers on their latching surface, it is no longer
necessary to form the lugs on the operationa I inter-
poser restoring bail. A small retaining clip may be
p laced on the operati ona I interposer restoring bai I
in the area where each interposer contacts the re-
1.11
1.12
4-2
store bail when being restored. This clip will pro-
vide approximately .015
1 '
more interposer restoring
motion. The clip is PN 1110093 and is described
as a feed roll retainer clip used on standard typebar
machines. This clip may be obtained through any
Joca I branch offi ce stockroom.
S. H. OPERATIONAL INTERPOSER SPRINGS
The operational interposer springs have been rede-
signed to provide greater spring tension and more re-
liable tripping of the operational cams. When fai l-
ures in the operational area are encountered and it
is suspected that these springs are fai ling to properly
trip the operational cams, all the interposer springs
should be replaced with the following new part
numbers.
NOTE: The operational cam pawls should be
checked frequent Iy for wear. They shou Id be re-
placed approximately every 15 months in machines
experi encing normal usage. Machi nes experienci ng
heavy usage such as 24 hour/day operati on wi II re-
quire that these pawls be replaced more frequently.
Part No.
150047
1134948
Descri pti on
Spri ng, spacebar interposer
Spring, operational interposer
(a II except space)
Note: Occasional malselections may also be
cm;sed due to failure of the interposer to trip the
space cam. This can happen if the space interposer
is tri pped off, trave Is to the rear, but does not tri p
the space cam. If the next pulse to the printer is to
the pri nt magnets, thi s pu Ise wi II start to activate
the pri nt magnets and then the interposer wi II tri P
the space cam openi ng C-5 and therefore cut the
pulse to the print magnets. This will cause such a
short duration of pulse on the print magnets that a
malselection will result due to improperly selected
latches.
S. H. BACKSPACE CAM PAWL WEAR
Backspace cam pawls may be checked for weal" dur-
ing inspection or on service calls by using this
method:
Hold the carrier and repeated Iy operate the back-
space. Worn pawls wi II slip on the cam and ratchet
and can be heard immediately.