Nokia Customer Care
Appendix A: RF Troubleshooting
Company Confidential
Copyright
©
2005 Nokia. All rights reserved
A-31
•
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
3.1.1.3.1.1 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.
3.1.1.3.1.1.1 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.
3.1.1.3.1.2 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.
3.1.1.3.1.3 Replace inductor L7516
•
If replacing does not help, replace GSM PA (N7502)
3.1.1.3.2 Are bias currents coming correctly to the GSM PA (N7502)?
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 GSM850/EGSM900 and “0” in GSM1800/GSM1900)
•
Measurements can be done with an oscilloscope and a VOLTAGE probe.
•
GSM850/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
4.6.4 "lcont_21/lcont_22 (DC offset 1.2V)"
when measured with an oscilloscope and a
probe. Check both currents.
Summary of Contents for RM-57
Page 391: ...www s manuals com ...
