Nokia 1508 Manual page 17

1508(RM-388)
Baseband Description and Troubleshooting
No Sound in Earpiece & Microphone Check (refer to MIC
headset, Audio PA Circuit design)
Enter the test mode 'LoopBack' by pressing test order #0000# then press 'calling
key' when the No Sound in Earpiece & Microphone message appears.
1. If the test result is normal, it indicates that the 'Loopback' circuit (receiver &
microphone) is OK in hardware connection; the bottom socket should be checked
whether it has been short circuited to the ground; If it is grounded, the mobile phone
software will detect that the earpiece is in the Insert Mode, which sets the mobile
phone in earpiece mode, and it means both of the earpiece and the microphone do
not work.
2. If the test result shows that the 'Loopback' is abnormal, the fault reason should
be picked up from the earpiece and the microphone. Dial 112 emergency call and
diagnose fault.
If the sound works, the microphone Mic is directed wrong, or it indicates the
receiver does not work properly.
3. In the case the Contact Connection is adopted between the earpiece and the Mic
of the mobile phone, test if the connection works.
If there is a fault in telephone receiver, first try to recover the earpiece by
•
performing the experiment described above. If it still doesn't work, Audio PA chip
or CPU chips may be damaged from poor welding or injury. The chips should
then be repaired by re-welding or replacement.
• If there is a fault in Microphone, first try to recover the earpiece by performing the
experiment described above. If it still doesn't work, Audio PA chip or CPU chips
may be damaged from poor welding or injury. T The chips should then be
repaired by re-welding or replacement.
Issue 1
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