Vhf Vco - Nokia NSW-6 Series Disassembly & Troubleshooting Instructions

NSW-6
Disassembly & Troubleshooting

VHF VCO

The VHF VCO signal is used to generate transmitter Intermediate fre-
quencies. The VHF VCO has two fixed frequencies. Operating frequency
is locked in Phase locked Loop, which is controlled by baseband.
Because the oscillator has two frequencies, it has also two different
switching modes. These modes are controlled by a BAND–signal. In
AMPS and TDMA800 modes the VHF frequency is 322.38 MHz and log-
ical level of BAND–signal is "HIGH". In TDMA1900 mode a higher inter-
mediate frequency is needed, so the operating frequency is increased to
392.46 MHz. The BAND– signal is set to logical level "Zero".
The VHF VCO output signal is fed to EROTUS LO–pin VV_in. Inside the
EROTUS, the signal is divided for the Phase detector and TX parts. Be-
fore injection to the I/Q–modulator, the frequency is divided by 2 .
Is oscillator
locked ?
Check oscillator
output level
at C744
P:
Check N770
Check PD1 at
C790
V=1–2 (LB)
=2.8–3.8 V (HB)
CHANGE
EROTUS!
Page 44
Y
OK
N
Check EROTUS (N700)
Y
(SCLK):2.8V
(SDATA):2.8V
(SENA1):2.8V
SENA is 0 during SCLK
and SDATA
N
N
Change N770
Y
N
Change V723
Y
E Nokia Mobile Phones Ltd.
PAMS Technical Documentation
Note!
The Oscillator is locked, when
the frequency is stable.
Note!
SENA1 = EROTUS PLL
SENA2 = 2G PLL (N870, pin 13)
Note!
Check all solderings and
missing components
Note!
Check all solderings and
missing components
Note!
Check all components and soldering
Issue 1 12/99