Troubleshooting Diagram For Gsm1900 Receiver - Nokia RH-30 Series Troubleshooting Instructions

Troubleshooting diagram for GSM1900 receiver

Phone in "Continuous" mode, AGC setting "12
ICQ: 343183001 QQ: 35070846 Email: Serviceic@yahoo.com.cn
Apply –90dBm
1960,06771
1842.86771MHz signal
from generator to anten-
na connector
Yes No
Oscilloscope at
RX_I /RXQ
Signal 160mVpp
DC offset 1.35V ***
Frequency 67.7kHz
Yes
GSM1900
GSM1800 RX chain
functional
Spectrumanalyzer
HELGA inputs
GSM1900
-89
–78 dBm
Oscilloscope
VR1,3...6 2.7V
Check HELGA serial
interface
(burst mode)
Spectrumanalyzer
4G VCO out
3920
3685.6MHz
∼–30 dBm (*
Check HELGA
N500
Figure 23: GSM1900 receiver troubleshooting
Yes
Change ge- Spectrumanalyzer
Antenna Switch out-
nerator level
put, GSM1900
to –50dBm
–88 dBm
Spectrumanalyzer
o RX_SAW_out
–90 dBm
Oscilloscope
LNA_VCC 2.6V
LNA_P 0 V
Check V802,
C826, Z802,
C829, C8097,
C808
o
Check Baseband
Yes
Synthesiszer trou-
bleshooting
Yes
o
No
Spectrumanalyzer
Antenna Switch input
–84 dBm
Yes
Oscilloscope
VANT_3 2.7VV
VANT_1/2 0V
Yes
Check Antenna
switch Z800
Yes
Oscilloscope
VR1,3...6 2.7V
Check HELGA serial
interface
(burst mode)
Yes
Check HELGA
N500
No
Check C831,
L811
No No
Oscilloscope
o o o o
Check HELGA se-
rial interface (burst
mode)
Yes
o
Check HELGA
N500
Check Baseband
o
Check Baseband
Yes
o All spectrumanalyzer reading
values are measured with 1
kohm passive probe (use
tweezers to connect the
probe ground to the nearest
PWB ground). Reading value
is represented without +26
dB compensation.
* Spectrumanalyzer
reading with 1 kohm
passive probe (right val-
ue add +26 dB)
* ** DC–level of RXI/RXQ in
continuous mode will decrease
slowly.
The original level can be resto-
red by rewriting gain set.
Check Base-
band