Nokia RM-42 Service Manual page 372

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•
Measurements can be done with an oscilloscope and a probe.
•
Connect the probe to C7515 (or C7598)
•
VR1RX voltage level should be continuous 2.65 - 2.86 V in WCDMA mode. Typical value is
2.7 V.
4.2.4.6.1.1 Hinku (N7500) regulator voltage VR1 ok?
• See section
4.2.4.6.1.2 Replace Hinku (N7500)
4.2.4.6.2 Replace RX VCO (G7500)
4.2.4.7 Is RX VCO RF-signal coming to the Hinku at all?
• WCDMA receiver has to be active before RX VCO's output frequency and output level can be
measured. Procedure is explained in section "Receiver troubleshooting".
• Measurements can be done with a spectrum analyser and an RF probe. Spectrum analyser centre
frequency should be set according the used RX channel (see section "Frequency mappings"). RBW
and VBW = 1 MHz, Span ≤ 200 kHz.
• Check the level of the VCO frequency in T7501 outputs. The level should be about -25...-35 dBm. If
the signal level is correct in the input (-20...-30 dBm) but output level is not as expected then
replace T7501.
4.2.4.7.1 Replace balun T7501
4.2.4.8 Is RX VCO frequency as expected?
• WCDMA receiver has to be active before RX VCO's output frequency and output level can be
measured. Procedure is explained in section "Receiver troubleshooting".
• Measurements can be done with a spectrum analyser and an RF probe. Spectrum analyser centre
frequency should be set according the used RX channel (see section "Frequency mappings"). RBW
and VBW = 1 MHz, Span ≤ 200 kHz.
• Connect the RF probe to the T7501 input.
• Check if the frequency of the RX 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 -20...-30 dBm.
4.2.4.8.1 RX VCO control voltage VC ok?
• WCDMA receiver has to be active before RX VCO control voltage VC can be measured. Procedure is
explained in section "Receiver troubleshooting".
• Measurement can be done with an oscilloscope and a probe.
• Connect the probe to R7501.
• RX VCO control voltage VC should be constant DC-voltage between 0.7 - 3.8 V. Voltage level should
A-104
"Hinku (N7500) regulator voltage VR1
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Appendix A: RF Troubleshooting
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