TROUBLESHOOTING
1. TV/CATV doesn't display
Check TU4002 Pin9(Video output)
Can you see the normal signal?
Yes
No
Could you measure voltage of 
TU4002 & IIC lines?
Are they all normal?
Yes
You should replace TUNER.
No
You should check power line & IIC lines.
Check the input(Pin63) of AV switch(IC5003). Can you see the normal waveform?
Yes
No
After checking the Power of AV switch you should decide to replace AV switch or not.
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
No
No
After checking the Power of AV switch you should decide to replace AV switch or not.
After checking the Power of LPF you should decide to replace LPF or not.
Check the output(Pin8) of LPF(IC4006). Can you see the normal waveform?
Yes
Check the input(PinH26) of BCM3550(IC4006). Measure waveform at C1010 because it’s more easy to check.
Can you see the normal waveform?
No
Yes
After checking the Power of LPF you should decide to replace LPF 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.
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