Brother LX-300 Service Manual page 163

Problem
b. Defective Is the black lead connector
control (SG) connected to CN13 on the
motor. Main PCB?
Are pulses output from
output ports P44 to P47 (Pin
45 to Pin 48) of the main
CPU#3?
When the output from
output ports P44 to P47 (Pin
45 to Pin 48) of the main
CPU#3 is High, is the output
from transistor array Q17 to
Q20 Low?
Is +24V DC applied to Pins
3 and 4 of connector CN13
on the Main PCB?
Conductivity in motor
harness assy?
Correct resistance value
(approx. 38 ohms) between
each phase of the SG motor
and the COM pin?
c. Defective Is the blue lead connector
trimming connected to CN5 on the
(TR-G) switch. Main PCB?
Is main CPU port P15 (Pin
22) at High level when leaf
switch SG assy is open?
When leaf switch SG assy
is shorted, is CN5 on the
Main PCB shorted?
Is main CPU port P15 (Pin
22) at Low level when CN5
on the Main PCB is
shorted?
When main CPU port P15
(Pin 22) is at Low level, is
this recognized by the main
CPU?
d. Defective T- No cutting occurs despite a
cutter. grating noise is heard?
Cutting position is correct
but cutting is incomplete?
Check Item
Motor harness assy
not connected.
Defective main
CPU#3.
Defective transistor
array Q17 to Q20.
Conductivity problem
in Main PCB.
Defective motor
harness assy.
Defective SG motor.
Leaf switch assy not
connected.
Conductivity problem
in Main PCB.
Defective pull-up
resistor R48.
Defective leaf switch
SG assy.
Conductivity problem
in Main PCB.
Defective series
resistor R44.
Defective main
CPU#3.
The T-cutter plate is
not installed.
The T-cutter plate is
not installed correctly.
Defective T-cutter
plate.
Cause Remedy
Correctly connect
the motor harness
assy.
Replace Main PCB
assy.
Replace Main PCB
assy.
Replace Main PCB
assy.
Replace motor
harness assy for SG
motor.
Replace SG motor.
Correctly connect
the leaf switch assy.
Replace Main PCB
assy.
Replace Main PCB
assy.
Replace leaf switch
SG assy.
Replace Main PCB
assy.
Replace Main PCB
assy.
Replace Main PCB
assy.
Install the T-cutter
plate.
Correctly install the
T-cutter plate.
Replace the T-cutter
plate.
7-13
See
Repair
Section
3.3.3
3.3.4
3.3.5
Replace
CPU#3.
3.3.3
Replace Q17
3.3.4
to Q20.
3.3.5
3.4.2
3.5.1
3.3.1
3.3.3
3.3.4
3.3.5
3.4
3.3.1
3.3.3
3.3.4
3.3.5
3.4
3.12
3.3.3
3.3.4
3.3.5
3.3.3
3.3.4
3.3.5
Replace R48.
3.4.2
3.5.1
3.3.1
3.3.3
3.3.4
3.3.5
3.4
3.12.1
Replace R44.
3.3.3
3.3.4
Replace
3.3.5
CPU#3.
3.4.2
3.5.1
3.3.1
3.3.1