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Appendix A: RF Troubleshooting
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.
4.3.2.1.1.1.1.1 Replace Vinku (N7501) or Hinku (N7500) or both
4.3.2.1.1.1.2 Retu ok?
4.3.2.1.2 R7521 and R7504 in place and working correctly?
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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 with
an ohmmeter.
4.3.2.1.3 VB_EXT voltage ok?
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Measurement can be done with an oscilloscope and a probe.
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Connect the probe to C7518.
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VB_EXT voltage should be 1.325 – 1.375 V. Typical value is 1.35 V.
4.3.2.1.3.1 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 ohmmeter
4.3.2.1.3.2 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 are
not short-circuited. If short-circuit is found replace capacitors mentioned above. If this does not
help go to the next step.
4.3.2.1.3.3 Replace Vinku (N7501) or Hinku (N7500) or both
4.3.2.1.4 Replace Vinku (N7501)
4.3.2.2 Is capacitor C7579 in WCDMA PA (N7503) bias line working correctly?
Icont_12 missing – C7579 short-circuited?
•
Check that component is in place and solder joints are ok
•
Disconnect the power supply from the phone and use an ohmmeter to check that the capacitor is
not short-circuited. If short-circuit is found replace the capacitor. If this does not help go to the
next step.
4.3.2.3 Replace Vinku (N7501) or WCDMA PA (N7503)
4.3.3 Are TX-IQ signals ok?
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