Nokia RM-94 Rf Troubleshooting Instructions page 35

RM-94
6(b) - RF Troubleshooting
Setup with Phoenix:
Band: GSM 1800
Mode: RX Continuous
Channel: 700
Spectrum analyzer
VCO out (G7500)
f = 3685.6 MHz
VCO
Vc of VCO = 2.1..2.6V
No
Spectrum analyzer
VCO out (G7500)
Some signal 3 - 4.4 GHz
Yes
Oscilloscope
VCO tuning voltage
Vc of VCO = 0V
Yes
Oscilloscope
PLL supply
(VR1=4.7V, VR5=2.78V)
It is important to note that the power supply VR3 of the VCTCXO is only switched off in the so
called 'Deep Sleep Mode' and the power supply VR7 of the VCO (G7500) is switched off in so
called 'Sleep Mode'.
Issue 1 04/2005
Yes PLL Block is functional
No
Oscilloscope
VCO supply
(VR7 = 2.78V)
No
Oscilloscope
Check RFBus signals
RFBusClk, RFBusData,
RFBusEn1 ok?
Yes
No
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Check R7503 and T7500.
Change VCO G7500
Yes
Check supply filter components:
C2203, R7500, C7500, C7501
No
Check UEM.
Change RF ASIC N7500
Yes
No Check baseband part.
Check loop filter components:
C7502, C7503, C7504, R7501, R7502
Short circuit to ground?
RF ASIC N7500 could be defective.
Check supply filter components:
C2232, C299, C7516, C7517, C7518
Check UEM.
Nokia Customer Care
Synthesizer
Fault Finding Tree
part 2
35