Siemens C25 Service Manual

Information and Communication Products
Communication Devices
V1.2 Page 15 of 34 ICP CD ST
D. Schnoor
8/99
5.4 Repair Documentation
5.4.1 Description of procedure:
5.4.1.1 Diagnosis
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.
5.4.1.2 Repair by component change
Use hot air to remove defective coil.
Avoid excessive heat!
Watch surrounding components!!
Resolder new coil afterwards
5.4.1.3 Repair by SW-Booting
Not possible!
5.4.1.4 Test
Retest handset after repair by checking the audio quality with the echo
loop of the testprogram.

Siemens C25 Specifications

General

Announced	1999
Display Type	Monochrome graphic
Talk Time	Up to 4 h
SIM	Mini-SIM
Call Records	10 dialed, 10 received, 10 missed calls
Loudspeaker	No
3.5mm Jack	No
Messaging	SMS
Clock	Yes
Alarm	Yes
Games	Yes
Languages	Multiple
Network	GSM
Weight	135 g
Battery Type	Removable NiMH battery
Alert Types	Monophonic ringtones