2. Video doesn't display

Check J5007 Pin2

Can you see the normal waveform?

Yes

Check the input(Pin1) of AV switch (IC5003). Pin1 is for video1,Pin8 is for video 2.

Can you see the normal waveform?

Yes

Check the output(Pin56) of AV switch(IC5003). Can you see the normal waveform?

Yes

Check the input(Pin1) of LPF(IC4006).

Can you see the normal waveform?

Yes

Check the output(Pin8) of LPF(IC4006). Can you see the normal waveform?

Yes

Check the input(PinH26) of BCM3550(IC1001). Measure waveform at C1010 because it’s more easy to check.

Can you see the normal waveform?

J5007 may have problem. Replace this Jack. No

 

After checking the Power of AV switch you should

No

decide to replace AV switch or not.

 

 

 

After checking the Power of AV switch you should

 

 

decide to replace AV switch or not.

No

 

 

 

 

 

 

 

 

 

After checking the Power of LPF you should

 

 

decide to replace LPF or not.

No

 

 

 

 

 

After checking the Power of LPF you should

No

decide to replace LPF or not.

 

This board has big problem because Main chip(BCM3550) have some troubles.

Yes After checking thoroughly all path once again, You should decide to replace BCM3550 or not.

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LG Electronics 20LS7D(C)-UB service manual Video doesnt display