Trouble Shooting Guide, Advanced
4/00021-3/FEA 209 544/25 C
Ericsson Mobile Communications AB
59(78)
At “ATMS – PCM – 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).
At “ATMS – CPU – AFMS” the chosen input signal should be seen at the oscilloscope (input
signal 1 kHz, 100 mVrms or 280mVptp sinus gives an output signal of 50mVrms or
150mVptp).
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 17.3.
If only the earphone part is out of order, go to section 17.4.
If only the ATMS input part is out of order, go to section 17.5.
If only the AFMS output part is out of order, go to section 17.6.
If only the CPU-loops are out of order, go to section 17.7.
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 17.8.
If none of the audio paths is working, go to section 17.9.
If all audio paths are working, but both the microphone and the earphone are out of order
during a connected call, go to section 17.10.
17.3 The microphone part is out of order
When there is a microphone fault it is 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 that the microphone has been replaced, but the fault
remains, so then the fault is at the board.
Open the phone and check for liquid damage.
No further action should be taken for a liquid damaged unit, send it on according to the
local company directives.
Power up the board and start it in EFRA with the test program.
Go to Audio / Audio.
Start Mic – AFMS.
Apply a sinus voltage of 50mV from the audio output (on the signal generator) directly to the
mic-pad 1 at the board.
Measure the voltage at R501, it should be 2.0 ± 0.10 V
DC
, then measure the voltage at R502,
it should be 1.3 ± 0.10 V
DC
.
Then measure the sinus signal at N500 (R502), it should be 50mV(rms).
If not the fault is probably N501.
Check the signal path on the board for fallen off or broken components, resold if necessary.
If there is a sinus signal (50 mV rms) at N500 the fault is probably due to N500, but it can
also be D600 or D500.
The reference voltages at N500 should also be measured, they should be :
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