Nokia 6680 RM-36 Service Manual page 296

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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).
• 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.
3.2.1.1.1.1 Replace Hinku (N7500)
3.2.1.1.2 Replace antenna switch Z7503
3.2.1.2 Are matching components in place and working correctly?
EGSM900: C7512, C7514 and L7504
A-50
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Appendix A: RF Troubleshooting