Appendix A: RF Troubleshooting
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A-83
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Check that the component is in place and solder joints are ok
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Disconnect the power supply from the phone and check R7503 resistance value with an ohmmeter
4.1.1.3.3.1.3.2 Capacitors C7518, C7520 and C7570 working correctly?
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Check that components are in place and solder joints are ok
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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.
4.1.1.3.3.1.3.3 Replace Vinku (N7501) or Hinku (N7500) or both
4.1.1.3.3.1.4 Replace Vinku (N7501)
4.1.1.3.3.2 Is capacitor C7579 in WCDMA PA (N7503) bias line working correctly?
Icont_12 missing – C7579 short-circuited?
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Check that component is in place and solder joints are ok
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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.
4.1.1.3.3.3 Replace Vinku (N7501) or WCDMA PA (N7503)
4.1.1.3.4 Replace PA (N7503)
4.1.1.4 Does duplex-filter (Z7502) get correct RF-power level from WCDMA PA (N7503)?
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WCDMA transmitter has to be active before measurements. Procedure is explained in section
“Transmitter troubleshooting”.
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Set TX power level to 0 dBm (Set start level “0” to Phoenix)
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Measurements can be done with a spectrum analyser and an RF probe. Remember to make correct
frequency setting to the spectrum analyser. Spectrum analyser centre frequency should be set
according the used TX channel (see section “Frequency mappings”).
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Spectrum analyser RBW = VBW = 10 MHz, Span
≤
2 MHz, sweep time 100 ms
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Connect the probe to Z7502 TX input. The RF level should be roughly -20…-30 dBm.
4.1.1.4.1 Replace isolator Z7505
4.1.1.5 Replace duplex-filter Z7502
4.1.2 Does WCDMA TX transmit enough RF-power and power levels otherwise ok?
4.1.2.1 Is Vinku ASIC (N7501) transmitting correct RF-power?
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WCDMA transmitter has to be active before Vinku’s output level can be measured. Procedure is
