NSW-5
Disassembly and Troubleshooting Instructions
PAMS Technical Documentation
Page 35
Issue 1 10/00
Nokia Mobile Phones Ltd.
TDMA 1900 RX
Apply 1960.02 MHz
(Ch 1000)–70 dBm
signal (no modulation)
to external antenna
connector (X991)
Check level of
IF2–sinal (450 kHz)
in RF/BB–interface
from resistor R798
P:
≅
–13 dBm
Check UHF VCO
control voltage from
capasitor C861
V: 1.0
…
4.0 V
Start synthesizer
troubleshooting
Y
N
N
Y
NOTE! If RX800 check is OK, then RX1900
troubleshooting should be concentrated only on
duplexer Z960 and frontend N721 area and
surrounding components.
TDMA 1900
RX–chain is OK.
Start baseband troubleshooting
(signal go next to COBBA IC N250)
C
heck 3 multiplier output
level (58.32 MHz)
from capasitor C745
P:
≅
–10
…
–20 dBm
N
N
Check level
(1960.02 MHz)
from duplex filter
(Z960) input
P:
≅
–70 dBm
Check level
from frontend (N721)
LNA input pin no.7
P:
≅
–70 dBm
Check level
from LNA output
(N721) pin no.10
P:
≅
–56 dBm
N
Change diplexer Z970
Note!
Check all soldering and
components in antenna
circuit before changing
N
Y
Y
Change duplex filter Z960
or coil L721
Note!
Check all soldering and
discrete components of
frontend.
Change frontend N721
Y
Note!
AGC2 is on
= gain is in high state
(~ 2.8 V at N721 pin no.9)
Check level from MXR
input (N721) pin no.12
P:
≅
0–2 dB less than at LNA
output pin no. 10
Change RX bandfilter Z726
Note!
Check all soldering
N
Y
N
Y
Start synthesizer
troubleshooting
Note!
Signal level