Wcdma Transmitter Frequency Correct - Nokia 6680 RM-36 Service Manual

Appendix A: RF Troubleshooting
4.1.2.4.1 Replace isolator Z7505
4.1.2.5 Replace duplex-filter Z502

4.1.3 WCDMA transmitter frequency correct?

• Connect a spectrum analyser to the module test jig RF connector.
• Set WCDMA Tx ON. Procedure is explained in section "Transmitter troubleshooting".
• Check if the frequency of the transmitter is as expected. If output signal is not found try to use
500 MHz span setting.
The correct TX frequency is shown in Phoenix "Tx Control (WCDMA)" window and can be found also
in see section "Frequency mappings". If the frequency is not found at all then go to
WCDMA TX transmit RF-power at
4.1.3.1 Is TX VCO frequency as expected?
• WCDMA transmitter has to be active before TX VCO's output frequency and output level can be
measured. Procedure is explained in section "Transmitter troubleshooting".
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"). RBW
and VBW = 1 MHz, Span ≤ 200 kHz.
• Connect the RF probe to the T7503 input. VCO shield has to be removed before measurement.
Remember to solder the shield back after the phone repairing. Quick VCO alive check can be done
without removing the RF shield. The RF probe should be placed as near the TX VCO output as possible
(Put the head of the probe carefully inside the VCO can through the holes of the shield). This method
can be used only to check that the TX VCO is alive. It won't expose if the T7503 is broken or the
output level of the VCO is too low. Remember to use low RF Attenuator value in the spectrum
analyser with this method.
• Check if the frequency of the TX VCO is as expected. If the VCO signal is not found try to use wider
span setting. The output level of the VCO should be about -25 dBm.
4.1.3.1.1 C7543, C7548 and L7517 ok?
• These components should be checked if TX VCO frequency is not stable and TX PLL frequency not
locked.
• Check that components are in place and solder joints are ok
• Disconnect the power supply from the phone and use an ohmmeter to check that inductor is
conducting DC.
4.1.3.1.2 TX VCO control voltage VC ok?
• WCDMA transmitter has to be active before TX VCO control voltage VC can be measured. Procedure
is explained in section "Transmitter troubleshooting".
• Measurement can be done with an oscilloscope and a probe.
all?"
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