Nokia RM-42 Service Manual

Also see for RM-42: Service manual

Contents

Nokia Customer Care Appendix A: RF TroubleshootingA-60Company ConfidentialCopyright © 2005 Nokia. All rights reservedboth output lines. If the signal level is correct in the input (about -20…-30 dBm) but output level isnot as expected then replace T7501.3.2.2.10.1 RX VCO G7500 output level high enough?• GSM receiver has to be active before RX VCO’s output frequency and output level can be measured.Procedure is explained in section “GSM RX chain activation for manual measurements”.• Measurements can be done with a spectrum analyser and an RF probe. Spectrum analyser centrefrequency should be set according the used RX channel (see section “Frequency mappings”).• Spectrum analyser RBW and VBW = 1 MHz, Span = 0, sweep time 1 ms. Notice that GSMtransmission has pulsed nature and VCO output power should be measured during RX is active(triggering needed). Another possibility is to use following settings: RBW = VBW = 1 MHz, Span200 kHz and sweep time at least 2.5 seconds.• 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 widerspan setting. Output level of the VCO should be about -20…-30 dBm.3.2.2.10.1.1 Replace RX VCO G75003.2.2.10.2 Replace balun T75013.2.2.11 VCTCXO frequency and output level correct?• Measurement can be done with an oscilloscope and a probe.• Connect the probe to C7529 (or C7582)• The frequency of the VCTCXO should be quite exactly 38.4 MHz and level about 0.5 - 0.9 Vpp.Example of the correct VCTCXO output signal is presented in figure 6.5.1 "VCTCXO Output (DC Offset1.24 V)".3.2.2.11.1 VXO-voltage ok? (=Vdig).• Measurement can be done with an oscilloscope and a probe• Connect the probe to C7560 (or C7526, C7513)• VXO-voltage should be about 2.5 V3.2.2.11.1.1 C7560, C7513, C7526 and C2214 ok?• Check that components are in place and solder joints are ok• Disconnect the power supply from the phone and use an ohmmeter to find out if the VXO-line isshort-circuited to the ground. If short-circuit is found replace C7560, C7513, C7526 and C2214. Ifreplacing does not help then go to the next steps.