LG 20LS7D(C)-UB - Manual (Page 17)

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4. RGB_PC doesn't display
Check input connect P7004.
Can you see the normal waveform?
P7004 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 RGBHV, you
should decide to replace these components 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 RGB 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 input of MST3361(IC7012).
Can you see the normal waveform? After checking the Power of MST3382M you
should decide to replace MST3382M 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.