Brother LX-300 Service Manual page 172

Problem
b. Defective Is the red lead connector
cartridge type connected to CN6 on the
detector main PCB?
(CSIZE3)
Is the cartridge leaf switch
switch
CSIZE3 pressed when an
A3 cartridge is inserted?
Is the cartridge leaf switch
CSIZE3 not pressed when
an A3 cartridge is inserted?
Is the cartridge leaf switch
CSIZE3 not pressed when
an A4 or A6 cartridge is
inserted?
Is main CPU port P14 (Pin
21) at High level when leaf
switch CSIZE3 is open?
When leaf switch CSIZE3 is
shorted, is CN6 on the Main
PCB shorted?
Is main CPU port P14 (Pin
21) at Low level when CN6
on the Main PCB is
shorted?
When main CPU port P14
(Pin 21) is at Low level, is
this recognized by the main
CPU?
Check Item
Leaf switch assy not
connected.
Incorrectly installed
leaf switch assy.
Incorrectly inserted
cartridge?
Incorrectly installed
leaf switch assy.
Conductivity problem
in Main PCB.
Defective pull-up
resistor R49.
Defective leaf switch
assy.
Conductivity problem
in Main PCB.
Defective series
resistor R45.
Defective main
CPU#3.
Cause Remedy
Correctly connect
the leaf switch assy.
Correctly install the
leaf switch assy.
Re-insert the
cartridge.
Correctly install the
leaf switch assy.
Replace Main PCB
assy.
Replace Main PCB
assy.
Replace leaf switch
C3 assy.
Replace Main PCB
assy.
Replace Main PCB
assy.
Replace Main PCB
assy.
7-22
See
Repair
Section
3.3.3
3.3.4
3.3.5
3.3.1
3.3.3
3.3.4
3.3.5
3.4
3.17
6.2
3.3.1
3.3.3
3.3.4
3.3.5
3.4
3.17
3.3.3
3.3.4
3.3.5
3.4.2
Replace R49.
3.5.1
3.3.1
3.3.3
3.3.4
3.3.5
3.4
3.17
3.3.3
3.3.4
Replace R45.
3.3.5
3.4.2
Replace
3.5.1
CPU#3.