Nokia Customer Care
Appendix A: RF Troubleshooting
A-70
Company Confidential
Copyright
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2005 Nokia. All rights reserved
3.5.2.1 Vinku (N7501) RB_EXT voltage ok?
•
See section
"Vinku (N7501) RB_EXT voltage ok?"
3.5.2.2 Are capacitors in GSM PA (N7502) bias lines working correctly?
EGSM: Icont_21 missing – Replace Vinku
Icont_22 missing – C7545 short-circuited?
GSM1800/GSM1900: Icont_31 missing – C7556 short-circuited?
Icont_32 missing – C7561 short-circuited?
•
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.
3.5.2.3 Replace Vinku (N7501)
3.5.3 Does GSM PA (N7502) get correct DET_SW_G -voltage from Vinku ASIC (N7501)?
•
GSM transmitter has to be active before DET_SW_G voltage can be measured. Procedure is
explained in section “Transmitter troubleshooting”.
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Measurement can be done with an oscilloscope and a probe.
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Connect the probe to C7595. Notice: C7595 is a non-assembled component so the probe should be
connected to the pad that can be still found from the PWB.
•
DET_SW_G voltage should be about 2.8 V while TX burst and 0 V otherwise.
3.5.3.1 Replace Vinku (N7501)
3.5.4 Are components in GSM power control loop in place and working ok?
R7516 and C7559
•
Disconnect the power supply from the phone and use an ohmmeter to check that C7559 is not
short-circuited. If short-circuit is found replace the capacitor.
•
Check R7516 resistance value with an ohmmeter and replace resistor if needed.
