LG 520SI, CB550BN TROUBLESHOOTING GUIDE

TROUBLESHOOTING GUIDE

- 14 -

BASIC GUIDE

FOLLOW

NO POWER

PROCEDURE

FOLLOW

NO RASTER

PROCEDURE

FOLLOW

NO VERTICAL
DEFLECTION

PROCEDURE

FOLLOW

NO CHARACTER,
NO CONTRAST

PROCEDURE

FOLLOW OTHER

PROCEDURES.

CHECK

SMPS SECONDARY

B+OUTPUT.

CHECK

HORIZONTAL

OUTPUT

WAVEFORM.

CHECK

VERTICAL OUTPUT

WAVEFORM.

CHECK

VIDEO OUTPUT

WAVEFORM.

NO

YES

YES

YES

YES

NO

NO

NO

- 15 -

1. NO POWER

NO POWER

TROUBLE IN
F901, R901,
D901, D902, D903, D904

TROUBLE IN
Q915, Q917, IC901,R902,
R914, D906, D907

TROUBLE IN
D921, D922, D924, D928
OR THEIR CONNECTED
COMPONENTS

TROUBLE IN
Q904, Q905, Q914
CIRCUIT

TROUBLE IN
OTHER PRIMARY CIRCUIT

TROUBLE IN
D906, D907, R906

CHECK C905

DC VOLTAGE?

CHECK

IC901?

CHECK

T901

PIN 4 ?

CHECK

SMPS SECONDARY

DC VOLTAGE ?

CHECK

Q914 EMITTER

VOLTAGE (5V)?

NO

YES

YES

YES

YES

YES

NO NO

NO

NO

6.3V, 14V,
55V, 76V

DC=MORE THAN 130V

- 16 -

2. NO CHARACTER

NO CHARACTER

CHECK

IC301 PIN 8 (8V)?

CHECK

IC301 PIN 2, 4, 6 ?

CHECK

IC301 PIN 11,

15, 18 ?

CHECK

R, G, B CATHODE

VOLTAGE ?

CHECK

VIDEO OUTPUT

Q302, Q312,

Q322 ?

TROUBLE IN
IC302 12V LINE

TROUBLE IN
PC SIGNAL,
C311, C331, C351

TROUBLE IN
IC301 CIRCUIT

TROUBLE IN
IC301 CIRCUIT

TROUBLE IN
VR302, VR312, VR322

VIDEO OUTPUT:

Q301~Q304,
Q311~Q314,

Q321~Q324

TROUBLE IN
CDT SOCKET

NO

YES

NO

NO

YES

YES

YES

YES

YES

YES

NORMAL=44~67V

NO

NO

CHECK

IC301 PIN 9 ?

FOLLOW

NO CONTRAST

PROCEDURE

NO

1.2v

CHECK

IC301 PIN 19 ?

TROUBLE IN
CLAMP CIRCUIT

NO