Nokia 6680 RM-36 Service Manual page 331

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.
4.1.2.1.2.1.1.1.2 Replace Vinku (N7501) or Hinku (N7500) or both
4.1.2.1.2.1.1.2 Retu ok?
4.1.2.1.2.1.2 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 R7521 and R7504 resistance values with
•
an ohmmeter.
4.1.2.1.2.1.3 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.
4.1.2.1.2.1.3.1 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
4.1.2.1.2.1.3.2 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.
4.1.2.1.2.1.3.3 Replace Vinku (N7501) or Hinku (N7500) or both
4.1.2.1.2.2 Replace Vinku (N7501)
4.1.2.1.3 Are TX-IQ signals ok?
• These current mode signals are not possible to measure, but are tested with self-tests. So if there
is no fail in 2.3 "ST_CDSP_TX_IQ_TEST" these signals should be ok. Otherwise Vinku (N7501) or
RAP3G (D2800) is faulty. Notice that it is not possible to replace RAP3G ASIC.
4.1.2.1.4 Is the TXC-signal coming to Vinku ASIC (N7501) OK? Is signal level correct?
WCDMA transmitter has to be active before TX control voltage TXC can be measured. Procedure is
•
explained in section "Transmitter troubleshooting".
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