Nokia RM-42 Service Manual
Also see for RM-42: Service manual
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Nokia Customer Care Appendix A: RF TroubleshootingA-34Company ConfidentialCopyright © 2005 Nokia. All rights reserved3.1.1.3.1.3 Replace inductor L7516• If replacing does not help, replace GSM PA (N7502)3.1.1.3.2 Are bias currents coming correctly to the GSM PA (N7502)?EGSM: Icont_21 and Icont_22GSM1800/GSM1900: Icont_31 and Icont_32• GSM transmitter has to be active before measurements. Procedure is explained in section“Transmitter troubleshooting”.• Set TX power level to the maximum (“5” in EGSM900 and “0” in GSM1800/GSM1900)• Measurements can be done with an oscilloscope and a VOLTAGE probe.• EGSM900:- Connect the probe to C7545 or C7544. Notice: C7544 is a non-assembled component so the probeshould be connected to the pad that can be still found from the PWB.- Typical full TX power bias currents (Icont_21 and Icont_22) should look somehow similar to figure6.5.4 "lcont_21/lcont_22 (DC offset 1.2V)" when measured with an oscilloscope and a probe. Checkboth currents.• GSM1800 or GSM1900:- Connect the probe to C7561 or C7556. Notice: C7556 is a non-assembled component so the probeshould be connected to the pad that can be still found from the PWB.- Typical full TX power bias currents (Icont_31 and Icont_32) should look somehow similar to figure6.5.5 when measured with an oscilloscope and a probe. Check both currents.3.1.1.3.2.1 Vinku (N7501) RB_EXT voltage ok?• See section "Vinku (N7501) RB_EXT voltage ok?"3.1.1.3.2.2 Are capacitors in GSM PA (N7502) bias lines working correctly?EGSM: Icont_21 missing – Replace VinkuIcont_22 missing – C7545 short-circuited?GSM1800/GSM1900: Icont_31 missing – C7556 short-circuited?Icont_32 missing – C7561 short-circuited?• 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.3.1.1.3.2.3 Replace Vinku (N7501) |
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