Text preview for : Troubleshooting.pdf part of LG CF25H30N LG model CF25H30N TV
Chassis MC-74A
Service Manual
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TROUBLESHOOTING
NO PICTURE/ NO COLOR
Is the CVBS signal at pin6 of IC512 normal? Yes Is the CVBS signal at pin16 of IC201 normal? Yes Are the CVBS signal at pin13, 17 of IC512 normal? Yes Is the Y signal at pin28 of IC512 normal? Yes Are the R-Y, B-Y signal at pin29, 30, 31, 32 of IC512 normal? Yes Are the R,G,B signal at pin19, 20, 21 of IC512 normal? Yes Are there R,G,B signal at pin8, 9, 10 of IC511? Yes Check the IK signal at pin18 of IC512. Yes Check CPT Board.
No Check IC512.
No Check/Replace IC201.
No Check/Replace IC201, Q201.
No Check/Replace IC512.
No Check/Replace IC512, IC590, IC591.
No Check/Replace IC512.
No Check/Replace IC511.
No Check the IK Line CPT Board.
NO TELETEXT
Check the voltage 12V of CT75. Abnormal Normal
Check the 12V line to be correct.
Abnormal
Check the voltage of 5V line.
Check/Replace ICT75. No
4.8~ 5.2V Check if video signal is input at pin8 of ICT74.
No
Check if video signal is input at pin16 of IC201. Yes Check the CVBS line.
Yes Check I2C Bus lines. (SDA, SCL)
Check/Replace IC201.
OK Check the R,G,B signal at pin15,16,17,19 of ICT74.
No
Check/Replace ICT74, XT75. No
Yes Check the R,G,B signal at pin9,11,13,16 of ICT76.
Check/Replace ICT76.
Yes
Check/Replace IC512.
NO PICTURE/NO SOUND (RASTER OK)
Is the Auto search operating?
Yes
No
No
Is the CVBS signal at pin6 of IC512 normal?
Check the voltage 5V,12V,33V SDA,SCL of TUNER. OK
NG
Check/Replace IC512,T114 Yes GO TO NO PICTURE Block NO SOUND Block OK
Check/Replace voltage, I2C Line.
Check pin15, 19 of IC12, IC20.
NO RASTER (SOUND OK)
Check the voltage of CPT Heater
Normal
Abnormal
Abnormal Check the voltage of 200V Line of T406
Check the voltage of HV,SCREEN of CPT
Check the Heater pulse at pin 9 of T406 Abnormal
Normal
Normal
Check/Replace T406
Check/Replace CPT Board
Check/Replace Connector, FR410, FR901
NO SOUND (PICTURE OK)
Check Sound system of MENU OSD 5.5/6.0/6.5 4.5
Is the voltag of pin24 of IC12 5V(High)? Yes
Is the voltage of pin24 of IC12 0V(Low)? Yes
A/V STEREO MODEL
Is the SIF signal of pin12 of ICS17 normal? (Sound Board)
No Check/Replace ICS17.
Yes Check if the Audio signal at pin55 of IC512 normal. Check if the Audio signal at pin24,25 of ICS11 normal. No Check/Replace pin1 of IC512, sound Board. Yes Check if the Audio signal at pin2,5 of IC620 normal. No Check/Replace ICS11,IC512,Q514,Q515. Yes Check the Audio signal at pin7, 11 of IC620 normal. No Check/Replace ICS11. Yes Check/Replace C664, C665, Speaker. No Check the voltage of pin10, sound MUTE of pin8 of IC620. Normal MUTE
No Check/Replace XS11, ICS11, ICS12, IC201.
Yes Check if the Audio signal at pin9, 13 of ICS11 normal.
No Check/Replace ICS11.
Yes Check if the Audio signal at pin3,5 of IC620 normal.
No Check the voltage of pin10, sound MUTE of pin8 of IC620.
Yes Check if the Audio signal at pin7,12 of IC620 normal.
Yes Check/Replace C632, C633, Speaker.
RF STEREO MODEL (A2/NICAM)
NO RASTER
Check +B voltage at D825 CATHODE (130VDC) Normal 0V
Is the voltage at pin12/37 of IC512 8V?
No Check the voltage 5V,12V,30V,40V line
Check F801
Open
Yes Does the square waveform from pin40 of IC512 appear?
OK Check the voltage of C808
Check/Replace F801 0V
No Check/Replace IC512
Yes Check I2C Bus lines (SDA, SCL)
Yes Is the waveform of collector of Q401 normal?
150~ 380V Check the voltage at pin 9 of IC801
Check/Replace D831~D834 Lower than 6V Check/Replace R805,R806,D807, Q800,ZD808, D805,IC801
No Check/Replace Q401,T451,R831
Yes 6~ 8V Is the waveform of collector of Q402 normal?
No Check/Replace Q402
Yes
Check/Replace IC802, D803, D806 Check if the secondary voltage are shorted
Check/Replace T406