User Guide

Nokia Customer Care

Appendix A: RF Troubleshooting

A-38

Company Confidential

• GSM transmitter has to be active before TX control voltage TXC can be measured. Procedure is

explained in section “Transmitter troubleshooting”.

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

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

• Connect the probe to C7549

• Typical TX control voltage TXC timing should look somehow similar to figure 6.5.2 “

TXC in GSM

mode (DC offset 0 V)” (EGSM900 TX power level 5) and voltage levels should be roughly:

- EGSM900: 1.8 V while TX burst and 0 V otherwise.

- GSM1800/GSM1900: 1.8 V while TX burst and 0 V otherwise.

• 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.

3.1.2.1.4.1 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

3.1.2.1.4.2 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.

3.1.2.1.4.3 Retu ok?

3.1.2.1.5 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 pad. 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.

3.1.2.1.5.1 C7595 working correctly?