LG FB915BU TROUBLESHOOTING GUIDE

TROUBLESHOOTING GUIDE

- 19 -

1. NO POWER

NO POWER

(POWER INDICATOR OFF)

TROUBLE IN
D901

TROUBLE IN
FUSE (F901)

TROUBLE IN

IC901 or Q902

TROUBLE IN
D923, D922, D931,
D924, D925, D927

TROUBLE IN
IC903

CHECK

FUSE OK?

CHECK

C912 (+) VOLTAGE?

(310VDC AT INPUT
VOLTAGE 110VAC)

NO

YES

YES

YES

NO

NO

NO

CHECK

Q902 DRAIN

WAVEFORM (SQUARE

WAVE COMES OUT?)

CHECK

D923, D922, D931,

D924, D925, D927

VOLTAGE?

YES

- 20 -

2. NO CHARACTER

CHECK

IC302 PIN 3, 8,12 (12V),

PIN 17 (5V)?

CHECK

IC302 PIN 2, 6,11 ?

CHECK

IC302 PIN 29, 32, 35 ?

TROUBLE IN
P302,
5V, 12V LINE

TROUBLE IN
PC SIGNAL,
SIGNAL CABLE, IC2001

TROUBLE IN

IC302

TROUBLE IN
CDT SOCKET

NO

YES

NO

NO

YES

YES

CHECK

R, G, B CATHODE

VOLTAGE?

TROUBLE IN

IC303

NO

YES

NO CHARACTER

- 21 -

3. NO RASTER

NO VIDEO

(POWER INDICATOR

GREEN or ORANGE)

CHECK

POWER INDICATOR

GREEN or ORANGE ?

CHECK

SCREEN CONTROL

KNOB OF FBT

CHECK

VOLTAGE AT

D924 CATHODE (195V)

D925 CATHODE (80V)

IC911 OUT (12V)

IC960 CATHODE

(6.3V)?

CHECK

IC271(MICOM) PIN 5

(5V), IC201 PIN 16

(12V)?

ROTATE SCREEN
CONTROL KNOB TO
CLOCKWISE

TROUBLE IN
IC271 (MICOM),
IC201 (T/BASE), TDA4856

TROUBLE IN
SECONDARY CIRCUIT
OF T901, T902

TROUBLE IN PRIMARY
CIRCUIT OF T901, T902

TROUBLE IN
D-SUB & 5-BNC
SIGNAL CABLE

ORANGE

MIN.
(Counter-clockwise)

GREEN

OK

YES

NO

YES

NO