Nokia RM-12 Troubleshooting Instructions page 29

RM-12
Troubleshooting diagram for GSM1900 receiver
Phone in "Continuous" mode, AGC setting "12".
Apply –90dBm
1960.06771MHz signal
from generator to
antenna connector
Yes
Osilloscope at RX_I
signal 160mVpp DC
offset 1.35***
Frequency 67.7kHz
Yes
Rx 1900 chain
functional
Spectrumanalyzer: No
HELGO inputs
GSM1900 –88dBm
Yes
Check LNA
output from C829
–84dBm
Yes
No
Oscilloscope:
VR1,3...6 2.7V
Check HELGO
serial interface
No
(burst mode)
Yes
Spectrumanalyzer:
4G VCO output
No
3920 MHz
~-30dBm*
Yes
Check HELGO
N7300
N500
Issue 1 11/2004
Figure 6: GSM1900 receiver troubleshooting
Note! Generator level can be set higher
if needed. Just note that levels will be
different in whole chain respectively.
No
Spectrumanalyzer:
Antenna Switch
outputs, GSM1900
SAW input -88dBm
Yes
Oscilloscope:
VANT_3 2.7V
VANT_1/2 0V
Check Antenna
Switch Z800
Spectrumanalyzer:
RX_SAW_out –
(C7108)
90dBm (C826)
C7110
No
Oscilloscope:
LNA_VCC 2.6
Check Balun
LNA_P 0V
Z7104
T701 output
C7111, C7112
C808, C807
Yes
Check
Balun
Check C808,
L7108, C7112
L805, C807
Check
Baseband
Synthesizer
troubleshooting
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CCS Technical Documentation
No
Spectrumanalyzer:
Antenna Switch
input –84dBm
Yes
No
Oscilloscope:Check
HELGO serial
interface (burst
mode)
Yes Yes
Z7100
No
Check Z806
Yes
Oscilloscope:
R7100
Check R800,
R7101, L7107
R810, L800
No
VR1,3...6 2.7V
Check HELGO
serial interface
(burst mode)
Yes
Yes
Check
C7111,
N7300
HELGO N500
No
Check
X7100
C809
No
Check
Baseband
Check HELGO
N500 N7300
Z7103
No
Check Baseband
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 value add +26dB)
*** DC-level of RXI/RXQ in
continuous mode will
decrase slowly. The original
level can be restored by
rewriting gain set
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