4. RGB_PC doesn't display

Check input connect P7004.

Can you see the normal waveform?

Yes

Check the input of Component switch(IC5001). Can you see the normal waveform?

Yes

No

No

P7004 may have problem. Replace this Jack.

After checking the input TR of RGBHV, you should decide to replace these components or

not.

Check the output of Component switch(IC5001). Can you see the normal waveform?

Yes

Check the input of MST3361(IC7012, Pin 6,9,12). Can you see the normal waveform?

Yes

No

No

After checking the Power of RGB switch you should decide to replace component switch or not.

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?

Yes

Check the input and output of BCM3550(IC1001). Especially you should check

The H,V sync and clock.

Can you see the normal waveform?

No

Yes

After checking the Power of MST3382M you should decide to replace MST3382M or not.

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.

- 17 -

Page 17
Image 17
LG Electronics 20LS7D(C)-UB service manual Rgbpc doesnt display