Brother LX-300 Service Manual page 173

15
Buzzer does not sound.
a. Defective buzzer circuit.
Problem
a. Defective Are 4 kHz pulses output
buzzer circuit from DV0 (Pin 20) on main
CPU#3?
Are correct voltages applied
across buzzer BZ1?
Buzzer BZ1 does not
sound?
Check Item
Defective main
CPU#3.
Defective resistors
R36 and R69.
Defective buzzer BZ1.
Cause Remedy
Replace Main PCB
assy.
Replace Main PCB
assy.
Replace Main PCB
assy.
7-23
See
Repair
Section
Replace
CPU#3. 3.3.3
3.3.4
3.3.5
Replace R36
3.4.2
and R69.
3.5.1
Replace BZ1.