LG 577LM, LM577B TROUBLESHOOTING GUIDE

TROUBLESHOOTING GUIDE

- 17 -

1. NO POWER

CHECK U22, U11.

CHECK

U22 PIN5 VOLTAGE

(5V) ?

NO

NO POWER

(POWER INDICATOR OFF)

CHECK ADAPTER,

AND FIND OUT

A SHORT POINT

AS OPENING

EACH POWER LINE

CHECK J1’S

VOLTAGE

(24V) ?

NO

CHECK T1’S PRIMARY

COIL (OPEN CHECK)

CHECK

U17 Voltage

(5V) ?

NO

U13’S PIN11

0V ?

CHECK U13, AND
CHECK 5VA LINE

CHECK IIC LINE

CONNECTION

(U3, U1)

CHECK U4’S VCC,

XTAL, RESET

IS U5 PIN12

VOLTAGE REPEATED

AS PULSE SHAPE ?

NO

YES

YES

YES

NO

YES

NO PROBLEM

NO

CHECK KEY CONTROL

CONNECTOR ROUTINE

- 18 -

2. NO RASTER (OSD IS NOT DISPLAYED) – INVERTER

CHECK MICOM INV

ON/OFF PORT.

J4 PIN5

5V?

NO

NO RASTER

(OSD IS NOT DISPLAYED)

CHECK ADAPTER

J4 PIN10

24V?

NO

1. CONFIRM BRIGHTNESS
OSD CONTRL STATE.

2. CHECK MICOM DIM-ADJ
PORT

J4 PIN1

5V?

NO

REPLACE

INVERTER ASS’Y

CHECK

PULSE AS

CONTACTING SCOPE

PROBE TO CAUTION LABEL.

(CONTACT PROBE TO

CAUTION LABEL.

CAN YOU SEE PULSE

AT YOUR

SCOPE?

NO

REPLACE CCFL LAMP

IN THE LCD MODULE

YES

YES

YES

YES

- 19 -

1. CHECK PIN34, 35
SOLDERING CONDITION

2. CHECK X1

3. TROUBLE IN U5

U5

POWER PINS

3.3V?

NO

CHECK U2, U24

U5 PIN34, 35

OSCILLATE

AS 14.3M?

NO

CHECK U5’S SOLDERING
CONDITION AND
CHECK CONNECTION LINE
FROM U5 TO J5

NO

TROUBLE IN CABLE

OR LCD MODULE

CHECK SOLDERING

STATE OF U16

IS APPEAR LOW

VOLTAGE SIGNAL

AT J4?

YES

YES

NO

CHECK U12

J4 PIN4

5V?

NO

YES

YES

YES

3. NO RASTER (OSD IS NOT DISPLAYED) – MX88L284

NO RASTER

(OSD IS NOT DISPLAYED)

J5

PIN2 IS 65MHz CLOCK?

PIN4 IS 48KHz H-SYNC?

PIN5 IS 60Hz V-SYNC?

PIN37 IS 48KHz H-SYNC?

IS PULSE APPEARED

AT SIGNAL PINS?

- 20 -

CHECK U101

U1 PIN3

2.5V?

NO

CHECK U17, +5V

U1

POWER PIN

5V?

NO

1. CHECK PC

2. CHECK SIGNAL CABLE
& D-SUB CONNECTOR
LINE

CHECK

R,G,B INPUT?

U1 PIN 12, 20, 28

NO

CHECK IIC LINE

CHECK

IIC PULSE ?

U1 PIN32, 33

NO

CHECK H-SYNC LINE
(D-SUB

→U8→MICOM

→U1 PIN95)

CHECK

CKREF(H-SYNC) INPUT?

U1 PIN94

NO

CHECK CKREF INPUT

CHECK

H-SYNC INPUT?

U1 PIN90?

NO

YES

YES

YES

YES

YES

YES

YES

NO RASTER

(OSD IS DISPLAYED)

4. NO RASTER (OSD IS DISPLAYED) – TDA8752BH

- 21 -

CHECK H-SYNC LINE
(D-SUB→U8→MICOM

→U1 PIN95)

CHECK

OE(H-SYNC)?

U1 PIN87

NO

CHECK SIGNAL LINE

FROM U5 PIN11

TO U1 PIN89

CHECK

CLAMP INPUT(H-SYNC)?

U1 PIN89

NO

CHECK SIGNAL LINE

FROM U1 PIN84

TO U4 PIN254

(1024x768/85Hz : 95MHz)

CHECK

CLOCK INPUT

(25MHz-95MHz SINEWAVE)?

U5 PIN207

NO

CHECK SIGNAL LINE

FROM U2 PIN80

TO U5 PIN203

CHECK

H-SYNC INPUT?

U5 PIN203

NO

YES

YES

YES

4. NO RASTER (OSD IS DISPLAYED) – TDA8752BH / MX88L284