User Guide

Nokia Customer Care

RM-1

RF Troubleshooting

Company Confidential

7A - 33

Issue 1

• 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 when measured with an oscilloscope and a probe. Check both currents.

• DCS1800 or PCS1900:

- 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 when measured with an oscilloscope and a probe. Check both currents.

3.1.1.3.2.1 Vinku (N7501) RB_EXT voltage ok?

• GSM transmitter has to be active before Vinku’s RB_EXT voltage can be measured.

Procedure is explained in section “General instructions for TX troubleshooting”.

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

• Connect the probe to R7521.

• RB_EXT voltage should be 1.325 – 1.375 V.

3.1.1.3.2.2 Are capacitors in GSM PA (N7502) bias lines working correctly?

EGSM: Icont_21 missing – Replace Vinku

Icont_22 missing – C7545 short-circuited?

DCS1800/PCS1900: 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.

3.1.1.3.2.3 Replace Vinku (N7501)

3.1.1.3.3 Replace PA (N7502)

3.1.1.4 Are control voltages VC1, VC2 and VC3 coming correctly to the antenna switch (Z7503)?

• Use “RF Controls” window in Phoenix test software to activate the GSM transmitter and to

select the wanted GSM band. Procedure is explained in chapter “General instructions for TX