Are Components In Gsm Power Control Loop In Place And Working Ok - Nokia RM-57 Service Manual

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Check that the TX power is not over the specification limits in following offsets (tables below).
-
If the measurement is performed with a spectrum analyser according above settings then
there may be 1 to 3 dB exceeding with some limit values. This is caused because above
settings are meant only for fast modulation spectrum checking and are not exactly done
according 3GPP specification.
GSM850/EGSM900/GSM1800:
Offset (kHz)
Limit (dBc)
GSM1900:
Offset (kHz)
Limit (dBc)
One example of measured GSM Modulation Spectrum in GSM850/EGSM900 band is presented
in figure
• If modulation spectrum is not as expected separate the phone into parts and place to the
module jig.

3.4.1 Are components in GSM power control loop in place and working ok?

R7516 and C7559
• Disconnect the power supply from the phone and use an ohmmeter to check that C7559 is
not short-circuited. If short-circuit is found replace the capacitor. Check R7516 resistance
value with an ohmmeter and replace resistor if needed.
100 200
+0,5 -30
100 200
+0,5 -30
6.5.8 "TX Modulation spectrum
Company Confidential
Copyright © 2005 Nokia. All rights reserved
250 400
-33 -60
250 400
-33 -60
(GSM)"..
Appendix A: RF Troubleshooting
≥ 600
< 1 800
-60
600 1 200
< 1 200 < 1 800
-60 -60
A-65