Nokia 6021 Service Manual
Issue 1 04/2005
COMPANY CONFIDENTIAL
35
Copyright © 2005 Nokia. All Rights Reserved.
RM-94
6(b) - RF Troubleshooting
Nokia Customer Care
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’.
called ‘Deep Sleep Mode’ and the power supply VR7 of the VCO (G7500) is switched off in so
called ‘Sleep Mode’.
Spectrum analyzer
VCO out (G7500)
VCO out (G7500)
f
VCO
= 3685.6 MHz
Vc of VCO = 2.1..2.6V
PLL Block is functional
Oscilloscope
VCO supply
VCO supply
(VR7 = 2.78V)
Spectrum analyzer
VCO out (G7500)
VCO out (G7500)
Some signal 3 - 4.4 GHz
Change RF ASIC N7500
Check loop filter components:
C7502, C7503, C7504, R7501, R7502
C7502, C7503, C7504, R7501, R7502
Short circuit to ground?
RF ASIC N7500 could be defective.
RF ASIC N7500 could be defective.
Check supply filter components:
C2203, R7500, C7500, C7501
Check UEM.
C2203, R7500, C7500, C7501
Check UEM.
No
Yes
Setup with Phoenix:
Band: GSM 1800
Mode: RX Continuous
Band: GSM 1800
Mode: RX Continuous
Channel: 700
Synthesizer
Fault Finding Tree
part 2
Fault Finding Tree
part 2
Oscilloscope
VCO tuning voltage
VCO tuning voltage
Vc of VCO = 0V
No
Yes
Oscilloscope
Check RFBus signals
Check RFBus signals
RFBusClk, RFBusData,
RFBusEn1 ok?
RFBusEn1 ok?
Yes
Check baseband part.
Check R7503 and T7500.
Change VCO G7500
No
Oscilloscope
PLL supply
PLL supply
(VR1=4.7V, VR5=2.78V)
No
Yes
No
Yes
Check supply filter components:
C2232, C299, C7516, C7517, C7518
C2232, C299, C7516, C7517, C7518
Check UEM.
No
Yes