Troubleshooting Tables - Brother LX-200 Service Manual

7.6 Troubleshooting Tables

1
Nothing happens when power switch is pressed. (LED indicator does not light.)
a. Abnormal input voltage.
b. Abnormal +5V DC supply.
c. Defective main CPU.
Problem Check Item
a. Abnormal input Are AC adaptor, Jack PCB,
voltage power harness correctly
connected?
Is fuse F1 on Main PCB
blown?
Is AC adaptor output voltage
normal (about 21V DC at
rated input)?
Is AC adaptor voltage applied
to connector CN13 on Main
PCB?
b. Abnormal +5V Is power supply IC#6 pin 10
DC supply output Low or switching?
When power supply IC#6 pin
10 output is Low, is transistor
Q10 ON?
When transistor Q10 is ON,
is transistor Q11 ON?
c. Defective main Is Reset (Pin 29) of the main
CPU CPU #1 High?
Is oscillator waveform output
from XIN (Pin 30) and XOUT
(Pin 31) of the main CPU?
Cause
Defective harness Connect harness
connection.
Blown fuse. Replace fuse.
Defective AC adaptor. Replace AC adaptor.
Defective Jack PCB. Replace Jack PCB.
Defective power Replace power
harness. harness.
Defective power supply Replace Main PCB
IC#6. assy.
Defective transistor Replace Main PCB
Q10. assy.
Defective transistor Replace Main PCB
Q11. assy.
Zener diode ZD4 is Replace Main PCB
shorted. assy.
Defective reset IC#2. Replace Main PCB
assy.
Defective oscillator Replace Main PCB
XT1. assy.
Defective main CPU#1. Replace Main PCB
assy.
7-5
Remedy Repair
Replace
IC#6.
Replace Q10.
Replace Q11.
Replace ZD4.
Replace Q11.
Replace
IC#2.
Replace XT1.
Replace
CPU#1.
See
Section
3.3.3
3.3.4
3.3.5
3.5.1
3.3.1
4.3.2
3.3.3
3.3.4
3.3.5
3.5.2
3.3.1
3.3.2
3.3.3
3.3.4
3.3.5
3.4.1
3.3.3
3.3.4
3.3.5
3.5.1