Uhf Synthesizer - Nokia NPC-1 Series Troubleshooting Instructions

PAMS Technical Documentation
4
Check components:
C740, C741, C742, R741,
R742, R743 and
C749, C750, L750
3
Check resonator
components:
V744, C745, L746,
C747, C748

UHF SYNTHESIZER

The UHF synthesizer consists of a external 2GHz UHF VCO, loop filter and integrated PLL
in Safari RF-IC. Safari T IC contains stages like counters, pre-scaler, divider by two, phase
and frequency comparator and a charge pump circuit which allows two operational
modes analog and digital. The UHF VCO Oscillation frequency is from 2009.1MHz to
2059.02MHz.
In AMPS & TDMA800, two GHZ UHF VCO frequency signal is first divided by two inside
SAFARI and then that divided signal is fed to mixers. The output frequency of the VCO
depends on the DC-control voltage which is controlled by PLL-circuit inside SAFARI.
Issue 1 10/01
TX VHF VCO
Figure 17: Fault tree:
5
Change
cascade amplifier
N750
OK
5.No OK
4.No
1
START HERE
Is oscillator locked
OK
to 361.08 MHz
3.No or 363.6 MHz
2.No OK
2
Check operating
voltage:
4.75 V
at R745
ãNokia Corporation
Troubleshooting Instructions
6
6.No
Change
OK
SAFARI
Yes
OK!
No
Check:
L751, R745
OK
NPC-1
Page 33