Nokia Customer Care
Appendix A: RF Troubleshooting
A-38
Company Confidential
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2005 Nokia. All rights reserved
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GSM transmitter has to be active before TX control voltage TXC can be measured. Procedure is
explained in section “Transmitter troubleshooting”.
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Set TX power level first to the maximum (“5” in EGSM900 and “0” in GSM1800/GSM1900)
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Measurement can be done with an oscilloscope and a probe.
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Connect the probe to C7549
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Typical TX control voltage TXC timing should look somehow similar to figure 6.5.2 “
(EGSM900 TX power level 5) and voltage levels should be roughly:
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EGSM900: 1.8 V while TX burst and 0 V otherwise.
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GSM1800/GSM1900: 1.8 V while TX burst and 0 V otherwise.
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Change the TX to the minimum power level (“19” in EGSM and “15” in GSM1800/GSM1900)
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Typical TX control voltage TXC levels should be now about:
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EGSM900: 1.0 V while TX burst and 0 V otherwise.
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GSM1800/GSM1900: 0.7 V while TX burst and 0 V otherwise.
3.1.2.1.4.1 R7514 in place and working correctly?
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Check that the component is in place and solder joints are ok
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Disconnect the power supply from the phone and check R514 resistance value with an ohmmeter
3.1.2.1.4.2 C7549 working correctly?
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Check that the component is in place and solder joints are ok
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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)?
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GSM transmitter has to be active before DET_SW_G voltage can be measured. Procedure is
explained in section “Transmitter troubleshooting”.
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Measurement can be done with an oscilloscope and a probe.
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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.
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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?
