Brother LX-300 Service Manual page 166

9
Document width cannot be detected correctly.
a. Defective Y-carriage (Y-CA) motor.
b. Defective sensor unit (YCA-F).
c. Defective Y-cutter arm.
Problem
a. Defective Y- Is the Y-CA motor harness
carriage (Y- connected to connector C14
CA) motor on the Main PCB?
Are pulses output from
output ports P40 to P43 (Pin
41 to Pin 44) of the main
CPU#3?
When the output from
output ports P40 to P43 (Pin
41 to Pin 44) of the main
CPU#3 is High, is the output
from transistor array #5
Low?
During High output (4V
min.) of the Main CPU#3
output port P54 (Pin 29), is
+24 V applied to the CDM
pin (Pin 5) of CN14?
Correct resistance value
(approx. 227 ohms)
between each phase of the
Y-CA motor and the COM
pin?
b. Defective Is the flat cable connected
sensor unit to connector CN11 (CN10)
(YCA-F). on the Main PCB?
Actuator Y cuts photosensor
when a document is
inserted?
Photosensor cut off when
no document is inserted?
Is photosensor PH1 on the
Y-CA sensor PCB working
correctly?
Normal Conductivity in Y-
CA sensor PCB flat cable?
c. Defective Y- Does the Y-cutter arm move
cutter arm when the Y-CA motor
rotates?
Y-cutter arm is caught
during its movement?
Is the Y-cutter arm
separated from the sensor
rail?
Check Item
Motor harness not
connected.
Defective main
CPU#3.
Defective transistor
array #5.
Defective transistor
#5.
Defective transistor
Q16.
Conductivity problem
in Main PCB.
Defective Y-CA motor.
Defective connection
of the flat cable.
Actuator Y incorrectly
installed.
Defective actuator Y.
Defective photosensor
PH1.
DisConductivity in flat
cable.
Y-cutter arm and
timing belt incorrectly
installed.
Foreign matter stuck
to Y-sensor rail, Y-
sensor shaft and Y-
cutter arm shaft.
The Y-cutter arm shaft
is incorrectly installed.
Cause Remedy
Correctly connect
the motor harness.
Replace Main PCB
assy.
Replace main PCB
assy.
Replace Main PCB
assy.
Replace Main PCB
assy.
Replace Main PCB
assy.
Replace the Y-CA
motor.
Correctly connect
the flat cable.
Replace the Y
sensor carriage.
Replace the Y
sensor carriage.
Replace the Y-CA
sensor PCB.
Replace the Y-CA
sensor PCB.
Correctly install the
timing belt.
Clean off the foreign
matter.
Correctly install the
Y-cutter arm shaft.
7-16
See
Repair
Section
3.3.3
3.3.4
3.3.5
Replace
CPU#3.
Replace
3.3.3
QA5.
3.3.4
3.3.5
3.4.2
3.5.1
Replace Q5.
Replace
Q16.
3.3.1
3.3.3
3.3.4
3.3.5
3.4
3.7
3.3.3
3.3.4
3.3.5
3.3.3
3.3.4
Replace
3.3.5
PH1.
3.7
3.8
Replace the
sensor
harness
750X4.
3.3.3
3.3.4
3.3.5
3.8