User Guide

CCS Technical Documentation
Company confidential RH-23
Issue 1 03/2004 Nokia Corporation. Page 27
Troubleshooting diagram for GSM1800 receiver
Phone in “Continuous” mode, AGC setting “12
Figure 21: GSM1800 receiver troubleshooting
A
pply –90dBm
1842.86771MHz signal
from generator to
antenna connector
Osilloscope at RX_I
signal 170mVpp
DC offset 1.35***
Fre
q
uenc
y
67.7kHz
Spectrumanalyzer
A
ntenna Switch
output GSM1800
–
52dBm
Spectrumanalyzer:
A
ntenna Switch
Input –50dBm
Spectrumanalyzer:
HELGO inputs
GSM900 –56dBm
Oscilloscope
VANT_1…3 0V
Oscilloscope:Check
HELGO serial
interface (burst
mode
)
Oscilloscope:
VR1,3…6 2.7V
Check HELGO
serial interface
(burst mode)
* Typically variates -+ 3dB.
A
ll spectrumanalyzer
reading values are
measured with 1 kohm
passive probe. Reading
value is represented without
attenuation compensation.
A
ttenuation of the passive
probe has to checked using
tuning pad. Typically
passive probe has >20dB
attenuation.
Spectrumanalyzer:
VCO output
3685.6MHz
~0dBm*
Check HELGO
N500
Check
Baseband
Check
C831
Rx 1800 chain
functional
Check
L806,L807
Check
Baseband
Synthesizer
troubleshooting
Check HELGO
N500
Check Antenna
Switch Z809
*** DC-level of RXI/RXQ in
continuous mode will
decrase slowly. The original
level can be restored by
rewriting gain set
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
No
No
No
No
No
No
No
Spectrumanalyzer:
SAW filter (Z807)
outputs -56dBm
Change
SAW Z807
Yes
No
Change
generator
level
to
–
50dBm
OK
No