Read LG 42SL90QD-CA (CHASSIS:LC91L) Service Manual online
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6. HDMI doesn’t display
Check input connect JK600, JK601,
JK602,JK603
Can you see the normal waveform?
Check DDC communication
lines(IC600,IC601,IC602,IC603)
YES
YES
NO
JK600, JK601, JK602,JK603
may have problem. Replace this Jack.
NO
After checking the Power of this chip, you
should decide to replace this or not.
YES
Check HDCP communication lines(IC107)
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.
Check the input/output data of HDMI
Switch (IC603) & DDC line
NO
After checking the Power of this chip, you
should decide to replace this or not.
YES
5. RGB PC doesn’t display
Check JK404 ,
Can you see the normal waveform?
NO
JK404
may have problem. Replace this Jack.
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.
YES
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