Fault Finding Chart For Gsm1800/Gsm1900 Transmitter - Nokia NEM-4 Series Troubleshooting Instructions

CCS Technical Documentation
goes through the directional coupler (one of the power control loop components) to the
Antenna Switch.
Antenna Switch
The Antenna Switch works as a diplexer between RX and TX Bands. Moreover, it partly
suppresses the harmonics generated by the PA. Mjoelner RF ASIC controls the antenna
switch by three voltages CONT1, CONT2 and CONT3. The following table shows the dif-
ferent states.
CONT1 CONT2
[Volt]
0
0
0
0
2.7

Fault finding chart for GSM1800/GSM1900 transmitter

Is signal at
DCS / PCS YES
Input of Z601
OK?
YES NO
Is VPD_1800
signal OK?
Replace
L801
Are Z601
NO
Control lines
as per table?
YES
Replace
Check RF
YES
Antenna
Connector
Switch
X602. OK?
NO
KEY
Replace RF
Connector.
Test With
Spectrum
Analyzer
If the Tx output is too high, then it is most likely that there is a problem within the Power
Control loop.
Mjoelner is receiving the Reference TXC from Baseband and not getting any feedback
Issue 1 09/2003
Company Confidential
CONT3
EGSM Rx
[Volt] [Volt]
0 0
0 0
0 2.7
2.7 0
0 0
Is signal on
YES Is TX Signal at
C823 OK?
DCS / PCS In on
R819 OK?
NO
YES
Replace PA
NO
Investigate
YES
Mjoelner
Test With
Oscilloscope
Copyright  2003 Nokia Corporation.
Company Confidential
DCS Rx PCS Rx
X
X
START
NO Is TX Signal
at L705 OK?
Are TX I & Q
Signals OK?
YES
Are TXP &
TXC OK?
TXC TXP
U/S U/S
Change Change
UEM UPP
Check / End
Inspect Action
NEM-4
RF Troubleshooting
DCS/PCS
EGSM Tx
X
X
YES Is Vr2 2.8V
on R720?
NO NO
NO
Check T701
Are Digital
Change UEM.
& Associated
I & Q Signals
Components.
OK at J213 &
OK?
J214
NO YES
Refer To Baseband
Fault Finding
Page 6(b)-85
Tx
X
YES