User Guide

Appendix A: RF Troubleshooting

Nokia Customer Care

Company Confidential

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• Change the TX to the minimum power level (“19” in EGSM and “15” in GSM1800/GSM1900)

• Typical TX control voltage TXC levels should be now about:

- EGSM900: 1.0 V while TX burst and 0 V otherwise.

• GSM1800/GSM1900: 0.7 V while TX burst and 0 V otherwise.

3.5.1.1 R7514 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 R514 resistance value with an ohmmeter

3.5.1.2 C7549 working correctly?

• Check that the component is in place and solder joints are ok

• Disconnect the power supply from the phone and check with an ohmmeter that C7549 is not

short-circuited.

3.5.1.3 Retu ok?

3.5.2 Does GSM PA (N7502) get correct bias currents? Is the level of bias currents ok?

EGSM: Icont_21 and Icont_22

GSM1800/GSM1900: Icont_31 and Icont_32

• GSM transmitter has to be active before measurements. Procedure is explained in section

“Transmitter troubleshooting”.

• Set TX power level to the maximum (“5” in EGSM900 and “0” in GSM1800/GSM1900)

• Measurements can be done with an oscilloscope and a VOLTAGE probe.

• EGSM900:

- Connect the probe to C7545 or C7544. Notice: C7544 is a non-assembled component so the probe

should be connected to the pad that can be still found from the PWB

- Typical full TX power bias currents (Icont_21 and Icont_22) should look somehow similar to figure

6.5.4 “Icont_21/Icont_22 (DC Offset 1.2 V)” when measured with an oscilloscope and a probe. Check

both currents.

• GSM1800 or GSM1900:

- Connect the probe to C7561 or C7556. Notice: C7556 is a non-assembled component so the probe

should be connected to the pad that can be still found from the PWB

• Typical full TX power bias currents (Icont_31 and Icont_32) should look somehow similar to figure

6.5.5 "Icont_31/Icont_32 (DC Offset 1.2 V)" when measured with an oscilloscope and a probe. Check

both currents.