LG 20LS7DC Service Manual page 15

2. Video doesn't display
Check J5007 Pin2
Can you see the normal waveform?
Check the input(Pin1) of AV switch (IC5003).
Pin1 is for video1,Pin8 is for video 2.
Can you see the normal waveform?
Check the output(Pin56) of AV switch(IC5003).
Can you see the normal waveform?
Check the input(Pin1) of LPF(IC4006).
Can you see the normal waveform?
Check the output(Pin8) of LPF(IC4006).
Can you see the normal waveform?
Check the input(PinH26) of BCM3550(IC1001).
Measure waveform at C1010 because it's more
easy to check.
Can you see the normal waveform?
No
Yes
No
Yes
No
Yes
No
Yes
No
Yes
Yes
J5007 may have problem. Replace this Jack.
After checking the Power of AV switch you should
decide to replace AV switch or not.
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.
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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