NEC LCD1550X Service Manual page 84

MPU may have any problem.
2. No Picture
2.1 Back Light Does Not Turn On (POWER-ON INDICATOR (Green) Is Blinking)
Is control
pulse for
NO
brightness of
back light
input into #7 of
J703?
YES
NO
Is approx. 3.3V
input #5 of J703?
YES
Is DC2.5V (D2.5V)
output from #8 of
IC602?
[D2.5V Line Circuit]
Voltage D2.5V Line Circuit/Schematic Diagram
YES
DC2.5V
ASIC may have any problem.
Please check the part below.
MC
NO
D2.5V line may have any problem. Please check the parts
below.
MAIN (Power)
ASIC
ASIC
----------
MAIN (ASIC)
Please check the part below.
ASIC
Protection circuit in inverter circuit may have any problem.
Please check the parts below.
Inverter
Inverter
Inverter
Inverter
Inverter
Inverter
Inverter
Inverter
Inverter
Inverter
Inverter
Inverter
Inverter
Inverter
Inverter
Inverter
Inverter
Inverter
MC
Inverter drive circuit may have any problem. Please check the
parts below.
Inverter
Inverter
Inverter
Inverter
Inverter
Inverter
Inverter
Inverter
Inverter
2
MPU IC102
D2.5V- generator- IC
IC602
ASIC
IC400
ASIC IC400
LCD panel
(back light)
Output- Tr
Q701
Output- Tr Q702
Output- Tr
Q703
Output- Tr
Q704
Output- trans
T701
Output- trans
T702
12V-OVP- Tr
Q707
12V-OVP- zener diode
D707
Output- F/B- zener diode
D717
Output- F/B- zener diode
D718
Output- F/B- zener diode
D719
Output- F/B- zener diode
D720
Output- F/B- IC IC701
Output- F/B- IC
IC702
Abnormal detector- Tr
Q717
Abnormal detector- Tr
Q718
Abnormal detector- Tr
Q711
Abnormal detector- thyristor
TH701
MPU
IC102
LCD panel
(back light)
OCP- fuse
F701
OCP- fuse
F702
Output- Tr
Q701
Output- Tr
Q702
Output- Tr
Q703
Output- Tr
Q704
Output- trans
T701
Output- trans
T702
Power output- IC
IC703