Samsung SGH-B300, Service Manual, Page: 23 / 56

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Flow Chart of Troubleshooting
10-11
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10-1-5. Microphone Part
10-1-6. Receiver Part
Is the soldered status of
microphone O.K?
Microphone does not work
Reassemble the microphone
Resolder or change
R400,R401,R402,R403,R404,R429,R430,
VR400,VR401,C400,C401,C402,C403
END
No
Yes
Yes
Yes
Yes
No
Is microphone ok?
No
Check U300
Check the reference voltage on mic path
C402 / C403
≒
2.0V ?
Yes
There is no sound from the Receiver
Is the terminal of
Receiver O.K ?
No
Replace the Receiver
Yes
No
Yes
Check U300,R427,R428
Is there any signals at
the pin# P11 and
pin#N12 of U300 ?
END
Yes
Is there any signals at
the pin# 5 and pin# 10
of U402 ?
Check U402
No
Yes
①