User Guide

NSW-4
Disassembly & Troubleshooting
PAMS Technical Documentation
Page 34
Issue 1 Final
Draft 08/00
 Nokia Mobile Phones Ltd.
Troubleshooting diagrams for TX
AMPS TX
Connect an RF–cable to the antenna interface and connect the cable to a
spectrum analyzer input. Start WinTesla–software and set the phone to
Analog mode. Set channel 383 and Powerlevel 2 and measure RF ouput
level. Please notice insertion loss of the cable and attenuations in the test
jig or antenna adapter. It is recommended to use an external attenuator to
avoid overloading the spectrum analyzer.
Check current
consumption
I: >700 mA
AMPS, PL2, CH383
Y
N
Check Antenna Circuit
and Duplex–filter.
Chort circuit in PA?
Press down PA
Inreasing current
consumption ?
Note!
Check all supply voltages and solderings
Check also N900 pin3 frequency and
input power. Should be > –8 dBm and
f = 997.68 MHz. If not start synth trouble
shooting (TX–LO is missing)
Change PA
Check possibility for
delamination
Check gain control
voltage at C720
V: >2.5 V
Y
N
Check PA input PWR
P: > 0 dBm
Change PA
Y
Y
N
N
Check Z901 filter
insertion loss
<4dB
Check C909, R905 and
C910
Y
N
Check TXC
V: >1.5 V
Y
Start Power control
troubleshooting
Check COBBA
TXCDAC
(BaseBand)
N
TX driver input power
P: > –20 dBm
Change driver N902
Y
N
Delamination means, that the
chip has loosened inside the
package during reflow.
In AMPS mode PA pin 16 bias–
Voltage should be > 2.2V.
N