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Appendix A: RF Troubleshooting
3.5 TX power vs. time ok?
This section means situation when GSM TX power levels are ok, but burst timing is not correct or power
changes during TX burst.
•
GSM transmitter has to be active before measurements. Procedure is explained in section
"Transmitter troubleshooting". Note! It is probably needed to change the Tx Data Type in
Phoenix to "Random" before this measurement can be performed.
•
Measurement can be done with a GSM transmitter tester or other GSM communication tester.
Attach the phone to the product specific test jig and the measurement device to the
RF-coupler. Coupler attenuation should be also taken into account during measurements.
If TX power vs. time is not as expected separate the phone into parts and place to the module
•
jig.
3.5.1 Is the TXC-signal coming to Vinku ASIC (N7501) OK?
•
GSM transmitter has to be active before TX control voltage TXC can be measured. Procedure is
explained in section "Transmitter troubleshooting".
•
Set TX power level first to the maximum ("5" in GSM850/EGSM900 and "0" in
GSM1800/GSM1900)
•
Measurement can be done with an oscilloscope and a probe.
•
Connect the probe to C7549
•
Typical TX control voltage TXC timing should look somehow similar to figure
mode (DC Offset 0 V)"
roughly:
GSM850/EGSM900: 1.8 V while TX burst and 0 V otherwise.
-
GSM1800/GSM1900: 1.8 V while TX burst and 0 V otherwise.
-
•
Change the TX to the minimum power level ("19" in EGSM and "15" in GSM1800/GSM1900)
•
Typical TX control voltage TXC levels should be now about:
GSM850/EGSM900: 1.0 V while TX burst and 0 V otherwise.
-
•
GSM1800/GSM1900: 0.7 V while TX burst and 0 V otherwise.
3.5.1.1 R7514 in place and working correctly?
•
Check that the component is in place and solder joints are ok
•
Disconnect the power supply from the phone and check R514 resistance value with an
ohmmeter
3.5.1.2 C7549 working correctly?
•
Check that the component is in place and solder joints are ok
A-68
(GSM850/EGSM900 TX power level 5) and voltage levels should be
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4.6.2 "TXC in GSM
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