LG 20LS7D(C)-UB - Manual (Page 16)

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3. Component doesn't display
Check J5004
Can you see the normal waveform?
J5004 may have problem. Replace this Jack.
Check the input of Component switch(IC5001).
Can you see the normal waveform?
After checking the input TR of component, you
should decide to replace component switch or not.
No
No
No
No
No
Yes
Yes
Yes
Yes
Yes
Check the output of Component switch(IC5001).
Can you see the normal waveform?
After checking the Power of component switch
you should decide to replace component switch or
not.
Yes
Check the input of MST3361(IC7012, Pin 6,9,12).
Can you see the normal waveform?
After checking the Power of MST3382M you
should
decide to replace MST3382M or not.
Check the output of MST3361(IC7012 ).
Can you see the normal waveform? After checking the Power of MST3361 you should
decide to replace MST3361 or not.
Check the input and output of BCM3550(IC1001).
Especially you should check
The H,V sync and clock.
Can you see the normal waveform? This board has big problem because
Main chip(BCM3550) have some troubles.
After checking thoroughly all path once again,
You should decide to replace BCM3550 or not.