42LG5000 (CHASSIS:LD84D) - LG TV Service Manual (repair manual). Page 27

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HDMI doesn't display
Check input connect J900 , J901, 
J902
Can you see the normal 
waveform?
Check DDC communication 
lines(IC900, IC901, IC903 Pin5,6)
Check the input of HDMI 
Seitch(IC902)
This signal is TMDS.
Can you see the normal waveform?
YES
YES
NO
J900 , J901, J902
may have problem. Replace this Jack.
Check the output of HDMI 
Switch(IC902).
Can you see the normal waveform?
YES
YES
NO
After checking the trace of TMDS lines and 
power of HDMI Switch, you should decide to 
replace HDMI Switch  or not.
NO
NO
After checking the Power of this chip, 
you should decide to replace this or not.
After checking the Power of HDMI
 
Switch you should decide to replace 
MST3361 or not.
YES
Check HDCP communication 
lines(IC902)
NO
After checking the Power of this chip,
 
you should decide to replace this or not.
Check the output  of Main IC(IC100).
Especially you should check 
The H,V sync and clock.
Can you see the normal waveform?
YES
NO
After checking the Power of Main
 
IC(IC100) you should decide to replace 
Main IC or not.
This board has big problem because 
Main IC(IC100) have some troubles.
After checking thoroughly all path once 
again, You should decide to replace 
Main Board or not.
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