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Trouble Shooting Guide, Advanced
At "ATMS – CPU – AFMS" the chosen input signal should be seen at the oscilloscope
(input signal 1 kHz, 100 mVrms or 280mVp-p sinus gives an output signal of 120mVrms or
340mVp-p).
Apply the signal with a zero ohm probe at J602: 2.
Measure it with a standard probe at J602: 1.
At "Mic – CPU – Earphone" you should hear your self, in the earphone, if you whistle or talk
into the microphone.
If only the microphone part is out of order, go to section 21.3.
If only the earphone part is out of order, go to section 21.4.
If only the ATMS input part is out of order, go to section 21.5.
If only the AFMS output part is out of order, go to section 21.6.
If only the CPU-loops are out of order, go to section 21.7.
If both the CPU-loops and the PCM-loop are out of order, but the side tone, ATMS – Earphone
and Mic - AFMS, is working, go to section 21.8.
If the Speaker mode part is out of order, go to section 21.9.
If the Microphone amplifier is out of order, go to section 21.10.
If none of the audio paths is working, go to section 21.11.
If all audio paths are working, but both the microphone and the earphone are out of order during
a connected call, go to section 21.12.
21.3 The Microphone part is out of order
When there is a microphone fault is it only the audio paths "Mic – AFMS" and "Mic – CPU –
Earphone" that is faulty. The other three audio paths should be working.
The trouble shooting below assumes the microphone of the phone has been replaced, but the
fault remains, so then the fault is at the board.
Open the phone and check for liquid damages.
No further action should be taken for a liquid damaged telephone.
Give the board power and start it in the test program.
Go to Audio / Audio Fig. 21.2.
Start Mic – AFMS:
It is needed to set the Speaker/ Mic gain in the
Gain control for each measurement, adjustable between 00 to 3C Fig. 21.2.
Measure the DC voltage at C850 +1.2 V
, C851 +1.7 V
, and the middle circuit board pad of
DC
DC
the microphone, X830: 1 +2.5 V
.
DC
If the voltage at C850 is too low, measure the resistance of it against ground >100 Kohms.
If the resistance is correct, the fault usually is due to N800 or its soldering, but in some cases it
can be due to D600.
If the resistance is too low, the fault probably is due to C850, but it can also be due to N800.
If the voltage at C851 is too low, measure the resistance of it against ground >1 Kohm.
4/00021-3/FEA 209 544/18 B
90(121)
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