User Guide

Nokia Customer Care

Appendix A: RF Troubleshooting

A-70

Company Confidential

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”.

• Measurement can be done with an oscilloscope and a probe.

• 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.