Nokia 6680 RM-36 Service Manual page 324

Mobile terminal
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Disconnect the power supply from the phone and check R7509 resistance value with an
ohmmeter.
Use an ohmmeter to find out also if the AFC-line is short-circuited to the ground. If short-circuit is
found replace C7533. If this does not help then go to the next steps.
4.1.1.1.11.2.2 VCTCXO ok?
Remove R7509. If AFC-voltage is correct after removing then replace faulty VCTCXO G7501 and
solder R7509 (new component) back to the PWB
4.1.1.1.11.2.3 Replace Retu
4.1.1.1.11.3 Replace VCTCXO G7501
4.1.1.1.12 Replace Vinku (N7501)
4.1.1.2 Is there RF-power in the WCDMA PA (N7503) input at all?
WCDMA transmitter has to be active before measurements. Procedure is explained in section
"Transmitter troubleshooting".
Set TX power level to 0 dBm (Set start level "0" to Phoenix)
Measurements can be done with a spectrum analyser and an RF probe. Remember to make correct
frequency setting to the spectrum analyser. Spectrum analyser centre frequency should be set
according the used TX channel (see section "Frequency mappings").
Spectrum analyser RBW = VBW = 10 MHz, Span ≤ 2 MHz, sweep time 100 ms
Connect the probe to Z7506 output. The RF level should be roughly -40...-48 dBm.
4.1.1.2.1 Is Vinku (N7501) output RF-signal coming correctly to the Z7506 (SAW filter)?
WCDMA transmitter has to be active before measurements. Procedure is explained in section
"Transmitter troubleshooting".
Set TX power level to 0 dBm (Set start level "0" to Phoenix)
Measurements can be done with a spectrum analyser and an RF probe. Spectrum analyser centre
frequency should be set according the used TX channel (see section "Frequency mappings").
Spectrum analyser RBW = VBW = 10 MHz, Span ≤ 2 MHz, sweep time 100 ms
Connect the RF probe to L7511. The RF-level should be about the same on both ends of the
inductor. Check the level with 0 dBm power level (Set start level "0" to Phoenix).
Power level "0" – Vinku output level should be about -40...-48 dBm
4.1.1.2.1.1 Inductor L7511 and resistor R7520 in place and working correctly?
Check that components are in place and solder joints are ok
Disconnect the power supply from the phone and check R7520 resistance value with an
A-78
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Appendix A: RF Troubleshooting

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