Ericsson A2618s - Page 58

Trouble Shooting Guide, Advanced
4/00021-3/FEA 209 544/25 C
 Ericsson Mobile Communications AB
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ATMS – CPU – AFMS: The input signal is taken from the ATMS pin (pin 11) of the system
connector, through N501.
The signal passes a Tx-filter (band pass 300- 3400 Hz) and is AD
converted in N500.
The data is sent as PCM code through PCMULD to D500 where the
signal is speech coded.
The speech-coded information is sent to the processor through
DSPULD for further coding.
The signal is fed back in reverse order. It is decoded in the processor,
sent back to D500 through DSPDLD for speech decoding.
Then it is sent to N500, through PCMDLD, for DA conversion in the
PCM decoder.
The signal is filtered and amplified, then connected through N501 to
the AMFS_RTS pin (pin 10) of the system connector.
Mic – CPU – Earphone: The input signal is taken from the microphone pads through N501.
The signal is amplified, passes a Tx filter (band pass 300- 3400 Hz)
and is then AD converted in N500.
The data is sent as PCM code through PCMULD to D500 where the
signal is speech coded.
The speech-coded information is sent to the processor through
DSPULD for further coding.
The signal is fed back in reverse order. It is decoded in the processor,
sent back to D500 trough DSPDLD for speech decoding.
Then it is sent to N500, through PCMDLD, for DA conversion in the
PCM decoder.
The signal is filtered and amplified, then connected to X850:11/12
troughBEARPandBEARM.
17.2 How to find the fault
The trouble shooting part assumes that the microphone-unit, the earphone and the
earphone-springs are faultless and correctly mounted.
Start the phone (assembled) in EFRA with the test program.
Go to Audio / Audio.
Test the five different audio paths.
An appropriate signal for the audio signal generator is 1 kHz and 100 mVrms or 280 mV
p-p sinus.
You can attach the signal with a zero-ohm probe.
At the test “ATMS – Earphone” you should hear the chosen input signal (1 kHz) in the
earphone.
At the test “Mic – AFMS” a whistle in the microphone should be seen as a sinus shaped curve
at the oscilloscope.