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7
Network Problems
7.1
Find out if the fault is related to RX or TX
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.
Make sure the antenna connection W1 is not mechanically damaged, unsoldered or dirty
(varnish, glue, oxide...).
Start the board in EFRA with the test program.
Go to Radio \ Sensitivity, measure the "RX-sensitivity".
The frequency of the RF-signal from the GSM test instrument must be in accordance with the
chosen channel.
At an input signal of -98 dBm the phase error should be PEAK 0-65 and RMS 0-14 deg.
The highest allowed frequency error is ±2000 Hz.
If all values are within the accepted limits the fault probably is due to the LO, go to chapter 8
("LO-fault").
If both the Peak phase error and the RMS phase error (sometimes even the frequency error)
are too large, it usually is due to a too large attenuation in the signal path.
Check the function of the transmitter, go to Radio/Radio adjustment/set TX switched and
set TX power step at 5 for EGSM and 0 for GSM1800.
Check that the output power is 28- 32 dBm at the antenna plate using the spectrum analyser.
We have used following settings on the spectrum analyser: CF- Channel frequency, SPAN- 0
Hz, RBW- 300 kHz, VBW- 100 kHz and Sweep- 0.8 ms.
If there is no or low output power, go to section 7.3.1.
If the transmitter signal is within the accepted limits, go to section 7.4 (Tx-freq).
If there is to high output power make a calibration.
If both the Peak- phase error and the RMS phase error are correct, but the frequency error is
large, go to chapter 9 ("VCXO").
4/00021-3/FEA 209 544/25 C
©
Ericsson Mobile Communications AB
Trouble Shooting Guide, Advanced
20(78)
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