Troubleshooting Diagram For Gsm1800 Receiver - Nokia RH-30 Series Troubleshooting Instructions

Troubleshooting diagram for GSM1800 receiver

Phone in "Continuous" mode, AGC setting "12
ICQ: 343183001 QQ: 35070846 Email: Serviceic@yahoo.com.cn
Apply –90dBm
1842.86771MHz signal
from generator to anten-
na connector
Yes No
Oscilloscope at RX_I
Signal 140mVpp
DC offset 1.35V ***
Frequency 67.7kHz
Yes
GSM1800 RX chain
functional
Figure 22: GSM1800 receiver troubleshooting
Yes
Change ge-
Spectrumanalyzer
nerator level
Antenna switch out-
to –50dBm
puts,
1800 LNA out
-88
–61 dBm
Yes
Spectrumanalyzer
o
HELGA inputs
GSM 1800
-89
–88 dBm
Yes
Oscilloscope
VR1,3...6 2.7V
o o o o
Check HELGA serial
interface
(burst mode)
Yes
Spectrumanalyzer
4G VCO out
3685.6
3769.6MHz
∼–30 dBm (*
Yes
Check HELGA
N500
No
Spectrumanalyzer
Antenna Swithc input
-84 dBm
Yes
Oscilloscope
VANT_1...3 0V
Yes
Check Antenna
Switch Z800
No
Check C838, C839,
L821. L 872,
C836, C837,
V801
No
Check Base-
band
No
Synthesiszer trou-
bleshooting
o
No
Check C831,
L811
No No
Oscilloscope Check Base-
o o
band
Check HELGA se-
rial interface (burst
mode)
Yes
o o
Check HELGA
N600
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.