Siemens C25 Service Manual page 47

5.4 Repair Documentation
5.4.1 Description of procedure:
5.4.1.1 Diagnosis
5.4.1.2 Repair by component change
5.4.1.3 Repair by SW-Booting
5.4.1.4 Test
V1.2
The 18µH coil is used in the step up converter which is generating a
5.4 V supply voltage for the power amplifier out of the 2.8V battery
voltage.
If the coil is mechanically damaged (broken) it produces heavy
interference with the acoustical elements of the C25 resulting in a loud
humming noise in the earpiece.
A broken coil can easily be diagnosed by trying to move it with two
fingers. If it moves, the core is broken and the coil has to be
replaced.
Use hot air to remove defective coil.
Avoid excessive heat!
Watch surrounding components!!
Resolder new coil afterwards
Not possible!
Retest handset after repair by checking the audio quality with the echo
loop of the testprogram.
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