Nokia RM-57 Service Manual page 266

Appendix A: RF Troubleshooting
3.2.1.1 Is Z7503 (antenna switch) working correctly?
• GSM receiver has to be active before measurements. Procedure is explained in section "GSM
RX chain activation for manual measurements".
• Connect an RF-generator to the GSM-antenna connector
Set RF-generator frequency as following:
•
GSM850: 881.66771MHz (Channel 190)
-
EGSM900: 942.46771 MHz (Channel 37)
-
GSM1800: 1842.86771 MHz (Channel 700)
-
GSM1900: 1960.06771 MHz (Channel 661)
-
Measurements can be done with a spectrum analyser and an RF probe. Remember to make
•
correct frequency settings to the spectrum analyser (Centre frequency should be set to the
same frequency as the RF-generator). RBW and VBW = 10 kHz, Span = 0 kHz, sweep time 5 ms.
• RF-signals in this measurement are pulsed and video triggering is needed in the spectrum
analyser (software dependent issue. With some phone softwares these signals are constant
in "Local" mode and triggering is not needed).
GSM850/EGSM900: Connect the probe to L7504. The RF level should be roughly -75 dBm
•
during RX period when input signal in GSM antenna connector is -50 dBm. RF-levels should be
about the same on both ends of the inductor. Remember to select the correct band also in
Phoenix.
• GSM1800: Connect the probe to L7505. The RF level should be roughly -85 dBm during RX
period when input signal in GSM antenna connector is -50 dBm. RF-levels should be about the
same on both ends of the inductor. Remember to select the correct band also in Phoenix.
• GSM1900: Connect the probe to L7506. The RF level should be roughly -85 dBm during RX
period when input signal in GSM antenna connector is -50 dBm. RF-levels should be about the
same on both ends of the inductor. Remember to select the correct band also in Phoenix.
3.2.1.1.1 Are control voltages VC1, VC2 and VC3 coming correctly to the antenna switch (Z7503)?
• Use "RF Controls" window in Phoenix test software to activate the GSM transmitter and to
select the wanted GSM band. Procedure is explained in section "Transmitter troubleshooting".
GSM RX activation is described in section "GSM RX chain activation for manual
measurements".
• Use an oscilloscope and probe to find out if antenna switch control lines are working
according to table shown below. "Hi" means that there is 2.4 – 2.8 V control voltage level in
the corresponding control line. "Lo" means levels 0 – 0.2 V. Remember to trigger the
oscilloscope because control voltages VC1, VC2 and VC3 are pulsed
• Connect the probe to correct test points to measure VC1, VC2 and VC3 voltages (check test
point locations, see section "Test point locations"). Notice: these test points are PWB pads for
three non-assembled capacitors.
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