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4.1.3 Checking (50, 100, and 155 Ipm)
Forms Jam Check
The forms jam check indicates that the carriage
tractor was told to move, but the paper did not
move. A light emitting diode detects the time
between holes in the paper. If no hole is de-
tected in eight lines, the forms jam check is
set.
Note:
A false forms jam check or a false printer
check can occur when chads (chips) are not
completely punched out of two successive holes
in the paper.
Belt Speed Check
This check indicates that either the type belt
failed to move within two seconds after the
start time, or the type belt lost motion after
being up-to-speed. Motion is considered lost if
there is a 25% reduction in operating speed. The
speed is determined by sensing the time between
timing marks on the type belt.
Carriage Sync Check
Two conditions can set this check:
1.
2.
If a carriage feedback pulse (carriage ad-
vance pulse) occurs when no carriage
motion was initiated.
If a carriage feedback pulse (carriage ad-
vance pulse) fails to occUr within 8 ms,
during carriage spacing.
Coil Current Check
An 8 ms timer is started when a hammer driver
is fired. The driver gates current through its
associated hammer coil. The 8 ms timer is used
to check for the possibility of a hammer driver
being on longer than 8
rns.
If this condition is
detected, power is dropped to the printer, and
the coil current check is set. The status of the
three coil current lines that are the input to the
coil current check is saved until the check is
cleared. This indicates which one of the three
hammer driver cards is failing.
Note:
If an even number of hammers on one
of the three hammer driver cards is on longer
than 8 ms, the coil current check is not set.
This is because the hammer drivers are checked
for an odd number of hammer drivers on with-
in anyone of three hammer driver cards.
Belt Sync Check
This check is set by three possible conditions:
1.
2.
3.
If a home pulse occurs when not expected.
If a home pulse fails to occur when expected.
If more than 1 bit is generated from the
bit ring at one time.
The timing for the home pulse is determined
by counting the number of print scans. This
count is compared with the character set size
(only one home pulse per character set).
Emitter Check
Once the type belt motor is up-to-speed, the
print subscan line is monitored to verify that
it is oscillating. If no change occurs during any
2 ms period, emitter check is set. This check
supplements the belt sync check, which can-
not detect a broken or stopped belt.
Data Check
Parity is maintained on the data in the print
buffer. If invalid parity is detected during a
print cycle, data check is set.
Hammer Parity Check
This check compares the number of hammers
selected to fire with the number actually fired.
If a mismatch occurs the hammer parity check
latch is set.
End of Forms Check
End of forms is checked on the first line
printed of each new form. If end of forms line
is active, the printer goes not ready.
Throat Closed Check
The printer is not ready if the print unit is
not latched in place to close the throat.
Cover Closed Check
The printer is not ready if the cover is open.
Unprintable Character Check
One or more of the characters requested to
print were not in the print image. Unprintable
character is checked entirely by the micropro-
gram. There is no hardware checking involved.
Setting this check is a programmer option.
Belt Printer
50, 100, and 155 Ipm
4-11
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