Nokia RM-57 Service Manual page 279

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3.2.3.1 Hinku (N7500) RB_EXT voltage ok?
• GSM receiver has to be active before Hinku's RB_EXT voltage can be measured. Procedure is
explained in section "GSM RX chain activation for manual measurements".
• Measurement can be done with an oscilloscope and a probe.
• Connect the probe to R7504.
• RB_EXT voltage should be 1.325 – 1.375 V.
3.2.3.1.1 VREFRF01-voltage ok?
Measurement can be done with an oscilloscope and a probe.
•
• Connect the probe to R7503.
• VREFRF01 voltage should be 1.325 – 1.375 V. Typical value is 1.35 V.
3.2.3.1.1.1 Desolder R7503. Is VREFRF01 voltage still wrong?
Remember to solder a new component to R7503 pads after measurement.
3.2.3.1.1.1.1 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
•
are not short-circuited. If short-circuit is found replace capacitors mentioned above. If this
does not help go to the next step.
3.2.3.1.1.1.2 Replace Vinku (N7501) or Hinku (N7500) or both
3.2.3.1.1.2 Retu ok?
3.2.3.1.2 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 R521 and R504 resistance values with
•
an ohmmeter.
3.2.3.1.3 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.
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Appendix A: RF Troubleshooting
A-61