Brother LX-300 Service Manual page 164

7
Abnormal X-cutter operation.
a. Defective X-cutter position switch.
b. Defective X-cutter DC motor.
c. Defective X-cutter.
Problem
a. Defective X- The X-cutter rotary cutter is
cutter position at the left or right end but
switch neither Pin 2 nor 3 is
continuous with Pin 1?
Alternatively, both Pin 2 and
3 are continuous with Pin 1?
Conductivity between Pins
1, 2, and 3 of the X-cutter
harness assy?
During X-cutter operation,
do main CPU#3 port P22
(Pin 5) and port P23 (Pin
80) switch to High level?
When main CPU port P22
(Pin 5) and port P23 (Pin
80) are at Low level, is this
recognized by the main
CPU?
b. Defective X- During normal output of the
cutter DC Main CPU #3 output ports
motor P64 to P67 (Pins 34 to 37),
do the outputs between the
FET array Q10 Pin 5 and
Pin 7 alternate between 0 V
and 24 V?
Conductivity between Pins 4
and 5 of the X-cutter
harness assy?
Normal resistance (approx.
30 ohms) between Pins 4
and 5 of the X-cutter
harness assy (DC motor
resistance value)?
c. Defective X- Does the rotary cutter rotate
cutter when the DC motor rotates?
Cutting of only halfway?
Check Item
Defective X-cutter
unit.
Defective X-cutter
harness assy.
Defective pull-up
resistors R54 and
R59.
Defective main
CPU#3.
Defective FET arrays
Q7, Q10.
Defective X-cutter
harness assy.
Defective X-cutter
unit.
Defective X-cutter
unit.
Defective X-cutter
unit.
Metal or other foreign
matter in the
laminated document.
Cause Remedy
Replace the X-cutter
unit.
Replace the X-cutter
harness assy.
Replace Main PCB
assy.
Replace Main PCB
assy.
Replace main PCB
assy.
Replace the X-cutter
harness assy.
Replace the X-cutter
unit.
Replace the X-cutter
unit.
Replace the X-cutter
unit.
Remove the foreign
matter and replace
the X-cutter unit.
7-14
See
Repair
Section
3.3.1
3.3.3
3.3.4
3.3.5
3.4
3.6.1
3.3.1
3.3.3
3.3.4
3.3.5
3.4
Replace R54
and R59.
3.3.3
3.3.4
3.3.5
Replace
3.4.2
CPU#3.
3.5.1
Replace Q7, 3.3.3
Q10. 3.3.4
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
3.6.1
3.3.1
3.3.3
3.3.4
3.3.5
3.4
3.6.1