Nokia RM-42 Service Manual page 321

Appendix A: RF Troubleshooting
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.
3.2.2.3.1.1.1.2 Replace Vinku (N7501) or Hinku (N7500) or both
3.2.2.3.1.1.2 Retu ok?
3.2.2.3.1.2 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.
3.2.2.3.1.3 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.
3.2.2.3.1.3.1 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
3.2.2.3.1.3.2 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.
3.2.2.3.1.3.3 Replace Hinku (N7500) or Vinku (N7501) or both
3.2.2.3.1.4 Replace Hinku (N7500)
3.2.2.3.2 Are capacitors in Hinku (N7500) regulator lines working correctly?
C7504, C7515, C7509, C7508, C7596, C7598 and C7505
• 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.
3.2.2.3.3 RX VCO G7500 ok?
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