Troubleshooting Diagram For Gsm850 Receiver - Nokia RH-30 Series Troubleshooting Instructions

Troubleshooting diagram for GSM850 receiver

Phone in "Continuous" mode, AGC setting "12"
ICQ: 343183001 QQ: 35070846 Email: Serviceic@yahoo.com.cn
Apply –90dBm
881,66771
942.46771MHz signal
from generator to anten-
na connector
Yes No
Oscilloscope at RX_I
170
Signal 700mVpp
DC offset 1.35V***
Frequency 67.7kHz
Yes
850
900RX chain
functional
Figure 20: GSM850 receiver troubleshooting
Yes
Change ge- Spectrumanalyzer
Antenna Switch
nerator level
outputs, GSM900
to –50dBm
–88 dBm
Yes
Spectrumanalyzer
o
HELGA inputs
GSM900
–89 dBm
Yes
Oscilloscope
VR1,3...6 2.7V
o
Check HELGA serial
interface
(burst mode)
Spectrumanalyzer
4G VCO out
3526.4
3769.6MHz
∼–30 dBm (*
Yes
o o
Check HELGA
N500
No No
Spectrumanalyzer
Antenna Switch
input
–84 dBm
Yes
No
Oscilloscope Oscilloscope :
Check HELGA
VANT_1...3 0V
serial interface
(burst mode)
Yes
Check Antenna
switch
Z800
No
Check L809
L810
No
Check Base-
band
No
Synthesiszer trou-
bleshooting
Check C831,
L811
No
Check Base-
o
band
Yes
o
Check HELGA
N500
All spectrumanalyzer reading
values are measured with
2.5 kohm passive probe (use
tweezers to connect the
probe ground to the nearest
PWB ground). Reading value
is represented without
+34 dB compensation.
* Spectrumanalyzer
reading with 1 kohm
passive probe (right val-
ue add +34 dB)
* ** DC–level of RXI/RXQ in
continuous mode will decrease
slowly.
The original level can be resto-
red by rewriting gain set.