RH-13
Troubleshooting
CCS Technical Documentation
Page 68
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Nokia Corporation
Issue 1 11/02
TX VHF VCO
The TX VHF VCO signal is used to generate transmitter Intermediate frequency. TX VHF
VCO has three fixed frequencies 358.08 MHz for lower band and TDMA 428.16 MHz and
GSM 426.4 MHz for upper band. Operating frequency is locked in Phase locked Loop and
frequency is divided by two before modulator.
Fault finding chart for TX VHF VCO
AMPS, CH383
-> TX VHF frequency 358.08 MHz
TDMA1900, CH1000
-> TX VHF frequency 428.16 MHz
GSM850, CH189
-> TX VHF frequency 356.4 MHz
GSM1900, CH661
-> TX VHF frequency 426.4 MHz
Figure 48: Fault finding chart for TX VHF VCO.
1 START HERE
Is oscillator locked
to 356.4, 358.08,
426.4
or 428.16 MHz
OK!
Yes
3
Check resonator
components:
V802, C850, L820,
C874, C865
4
Check components:
C853, C852, C851,
R810, R809, R821 and
C841, C873, L828
2
Check operating
voltage:
4.75 V
at R833
Check:
L819, R833
No
OK
5
Change
cascade amplifier
N811
2.No
OK
3.No
OK
4.No
OK
5.No
OK
6
Change
SAFARI
6.No
OK