LG KS20 - Headset Path

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Only for training and service purposes
4. TROUBLE SHOOTING
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4.18 Headset path
MSM7200 HPH_R, HPH_L → C409, C406 → HEADSET AMP(U402) → R405, R404 → FB301,
FB300 → CN300 (MMI Connector)→
Start
Connect the phone to network
equipment and setup call.
Setup 1KHz tone out
and insert headset.
Can you hear the tone?
Change the Headset
YES
NO
END
Sine wave appears at
FB301/FB300?
YES
NO
Check an U100 SMT status
by X-ray
Exchange U100 or
Change the Main board
And Retest