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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.
4.1.3.1.2.2.1.1.2 Replace Vinku (N7501) or Hinku (N7500) or both
4.1.3.1.2.2.1.2 Retu ok?
4.1.3.1.2.2.2 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.
4.1.3.1.2.2.3 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.
4.1.3.1.2.2.3.1 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
4.1.3.1.2.2.3.2 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.
4.1.3.1.2.2.3.3 Replace Vinku (N7501) or Hinku (N7500) or both
4.1.3.1.2.2.4 Replace Vinku (N7501)
4.1.3.1.2.3 Balun T7503 ok?
•
WCDMA transmitter has to be active before TX VCO's output level can be measured. Procedure is
explained in section "Transmitter troubleshooting".
•
Measurements can be done with a spectrum analyser and an RF probe. Spectrum analyser centre
frequency should be set according the used TX channel (see section "Frequency mappings"). RBW
and VBW = 1 MHz, Span ≤ 200 kHz.
•
Check the level of the TX VCO frequency in T7503 outputs. The level should be about -30...-35 dBm
in both output lines. If the signal level is correct in the input (about -25 dBm) but output level
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