User Guide

Nokia Customer Care

Appendix A: RF Troubleshooting

A-42

Company Confidential

3.1.2.3.1 GSM PA (N7502) operating voltage ok?

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

• Connect the probe to C7593

• Voltage level should be 3.05 – 5.4 V. Typical value is 4.0 V.

3.1.2.3.1.1 PA operating voltage VBAT_PA ok?

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

• Connect the probe to C7569 (or C7564, C7583)

• Voltage level should be 3.05 – 5.4 V. Typical value is 4.0 V.

3.1.2.3.1.1.1 Ferrite Z7500 ok?

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

• Disconnect the power supply from the phone and use an ohmmeter to check that inductor is

conducting DC.

3.1.2.3.1.2 C7593 ok?

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

• 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.

3.1.2.3.1.3 Replace inductor L7516

• If replacing doesn’t help then replace GSM PA (N7502)

3.1.2.3.2 Are bias currents coming correctly to the GSM PA (N7502)? Level 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