Nokia 6680 RM-36 Service Manual page 288

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• 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
both currents.
• GSM1800 or GSM1900:
Connect the probe to C7561 or C7556. Notice: C7556 is a non-assembled component so the probe
-
A-42
"Icont_21/Icont_22 (DC Offset 1.2 V)" when measured with an oscilloscope and a probe. Check
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Appendix A: RF Troubleshooting