Nokia RM-42 Service Manual

Also see for RM-42: Service manual

Contents

Appendix A: RF Troubleshooting Nokia Customer CareCompany ConfidentialCopyright © 2005 Nokia. All rights reservedA-95• 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 capacitors arenot short-circuited. If short-circuit is found replace capacitors mentioned above. If this does nothelp go to the next step.4.1.3.1.2.2.1.1.2 Replace Vinku (N7501) or Hinku (N7500) or both4.1.3.1.2.2.1.2 Retu ok?4.1.3.1.2.2.2 R7521 and R7504 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 R7521 and R7504 resistance values withan ohmmeter.4.1.3.1.2.2.3 VB_EXT voltage ok?• Measurement can be done with an oscilloscope and a probe.• Connect the probe to C7518.• VB_EXT voltage should be 1.325 – 1.375 V. Typical value is 1.35 V.4.1.3.1.2.2.3.1 R7503 in place and working correctly?• Check that the component is in place and solder joints are ok• Disconnect the power supply from the phone and check R7503 resistance value with an ohmmeter4.1.3.1.2.2.3.2 Capacitors C7518, C7520 and C7570 working correctly?• 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 capacitors arenot short-circuited. If short-circuit is found replace capacitors mentioned above. If this does nothelp go to the next step.4.1.3.1.2.2.3.3 Replace Vinku (N7501) or Hinku (N7500) or both4.1.3.1.2.2.4 Replace Vinku (N7501)4.1.3.1.2.3 Balun T7503 ok?• WCDMA transmitter has to be active before TX VCO’s output level can be measured. Procedure isexplained in section “Transmitter troubleshooting”.• Measurements can be done with a spectrum analyser and an RF probe. Spectrum analyser centrefrequency should be set according the used TX channel (see section “Frequency mappings”). RBWand VBW = 1 MHz, Span ≤ 200 kHz.• Check the level of the TX VCO frequency in T7503 outputs. The level should be about -30…-35 dBmin both output lines. If the signal level is correct in the input (about -25 dBm) but output level