Nokia RA-8 Rf Description And Troubleshooting page 43

RA-8
7 - RF Description and Troubleshooting
Troubleshooting diagram for synthesizer
Setup with Phoenix:
Active Unit: Rx
Mode: Continuous
Channel:
190 (GSM850)
37 (GSM900)
700 (GSM1800)
661 (GSM1900)
Spectrum analyzer
Check with RF probe
VCO (G7500) out signal:
-3526.4MHz(GSM850)
-3769.6MHz(GSM900)
-3685.6MHz(GSM1800)
-3920MHz(GSM1900)
Level > -10dBm *
OK?
Yes
PLL Block is functional
Check loop filter components:
C7503, C7504, C7505, R7501, R7502
R7501, R7502
Wrong writing on RFBus (see BB part)
Wrong writing on RFBus (see BB part)
If ok change RF ASIC N7500
If ok, change RF ASIC N7500
Issue 1 11/05
Troubleshooting diagram for synthesizer
Oscilloscope
No
VCTCXO Supply
VR3=2.78V
Yes
Oscilloscope
VCTCXO output at G7501
26MHz,app.0.8Vpp
Yes
Oscilloscope
VCO supply
VR7 = 2.78V, VR5=2.78V,
VR1=4.7V
Yes
Spectrum analyzer
VCO (G7500) out
Some signal 3-4.4 GHz
Yes
C7502, C7519,
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Check supply filter components :
No
Fault is in non-reworkable
C2232, C7590.
component. Refer to
Check UEM and SW.
current BR handling guidance.
No
G7501 defective or short
Circuit to GND
Check supply filter components:
R7500, C7501, C7560, C2230, C7551,
No
R7500, C7501, C7500, C7505
C7552, C7553
Check UEM and Software.
No
Check VCO G7500,
Balun T7500
* When 1 kOhm passive probe is used,
Correct the measurement by +26dB
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43