LG CF25A50T Troubleshooting Guide

Troubleshooting Guide

NO RASTER

Check +B voltage at J405

Is the voltage at pin8,37

of IC501 8V?

Does the square

waveform from pin40 of

IC501 appear?

Is the waveform of

collector of Q451 normal?

Is the waveform of

collector of Q452 normal?

Check/Replace

T701

Check

Fuse of AC line

Check the voltage of

C808, C809

Check the voltage

of pin9 of IC801

Check/Replace

IC803, D835, D829

Check the 12V, 5V lines are

shorted.

Check/Replace

IC501

Check/Replace

Q451, T451, R452

Check/Replace

Q452

Check the voltage 5V,

12V lines

Check I2C BUS lines

(SDA, SCL)

Check/Replace

Fuse, D801, IC801

Check/Replace

D801

Check/Replace

D802, D805, D807,

Q801, IC801

Normal

Yes

Yes

Yes

Yes

No

No

No

No

OK

OK

254~380V

Lower than 6V

Open

0V

0V

NO SOUND

(PICTURE OK)

Check the Audio signal of

pin12 of IC101 normal

Check the Audio signal of

pin55 of IC601 normal

Check/Replace

Q605, AM line

Check whether Sound

system of MENU OSD

is correct or not

Is the SIF signal of

pin20 of IC101 normal?

Are the Audio signal of

pin28, 29 of IC601 normal?

Are the Audio signal of

pin2, 5 of IC651 normal?

Are the Audio signal of

pin7,11 of IC651 normal?

Check/Replace

C660, C664, Speaker

Set correct Sound

system

Check/Replace

IC101

Check/Replace

X601, IC601, IC602

Check Ro, Lo lines

Check the voltage

of pin10 of IC651

Check/Replace

IC101

NO

Yes

No

Yes

Correct

Yes

Yes

Yes

Yes

Incorrect

No

No

No

No

(No AM Sound) (No NICAM or FM Sound)