Rx Vhf Vco - Nokia NPC-1 Series Troubleshooting Instructions

PAMS Technical Documentation
2
OK
Change
VCTCXO 2.No

RX VHF VCO

The RX VHF VCO signal is used to generate receiver Intermediate frequency. RX VHF VCO
has one fixed frequency 271.08 MHz. Operating frequency is locked in Phase locked Loop.
RX VHF VCO output signal is fed to SAFARI. Inside the SAFARI signal is divided for Phase
detector and RX parts. Before I/Q-modulator frequency is divided by 2.
Fault finding chart for RX VHF VCO
Measure oscillator frequency over L730 coil. Do not connect probe to pads!
AMPS, CH383
Issue 1 10/01
Figure 15: Fault tree: 19.44 MHz oscillator
START HERE!
Is VCTCXO
oscillating?
19.44MHz
1.No OK
1
Check voltage
C792
2.78 V
No OK
Check resistor
R792
ãNokia Corporation
Troubleshooting Instructions
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NPC-1
Page 31