LG KF750 Service Manual page 114

Connect the phone to network
Equipment and setup call
Setup 1KHz tone out
Does the sine wave appear
1
Does the sine wave appear
2
Does the sine wave appear
3
Does the sine wave appear
4
at EAR(+) PAD in LCD FPCB?
Can you hear sine wave
5
out of a speaker ?
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Only for training and service purposes
START
at C531, C532?
YES
at U500 ?
YES
at U501 ?
YES
YES
YES
END
4. TROUBLE SHOOTING
NO
Change the main board
NO
Change the U500
NO
Change the main board
NO
Change the LCD FPCB
NO
Change the Speaker
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The sine wave not appear
LGE Internal Use Only