Nokia RM-42 Service Manual page 359

Appendix A: RF Troubleshooting
Measurements can be done with an oscilloscope and a probe.
•
Connect the probe to C7579
-
WCDMA PA bias current Icont_12 should look as a constant 2.5 - 2.6 V DC-voltage with all power
-
levels.
Connect the probe to C7576 pad. Notice: C7576 is a non-assembled component so the probe
-
should be connected to the pad that can be still found from the PWB.
WCDMA PA bias current Icont_11 should look as a constant 2.5 - 2.6 V DC-voltage with all power
-
levels.
4.1.2.3.3.1 Vinku (N7501) RB_EXT voltage ok?
WCDMA transmitter has to be active before Vinku's RB_EXT voltage can be measured. Procedure is
•
explained in section "Transmitter troubleshooting".
• Measurement can be done with an oscilloscope and a probe.
• Connect the probe to R7521.
RB_EXT voltage should be 1.325 – 1.375 V.
•
4.1.2.3.3.1.1 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.
4.1.2.3.3.1.1.1 Desolder R7503. Is VREFRF01 voltage still wrong?
• Remember to solder a new component to R7503 pads after measurement.
4.1.2.3.3.1.1.1.1 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.
4.1.2.3.3.1.1.1.2 Replace Vinku (N7501) or Hinku (N7500) or both
4.1.2.3.3.1.1.2 Retu ok?
4.1.2.3.3.1.2 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 R7521 and R7504 resistance values with
an ohmmeter.
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