Nokia 7250, 7250i Service Manual

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Apply –90dBm
1842.86771MHz signal
from generator to anten-
na connector

Oscilloscope at 
RX_I /RXQ
Signal 160mVpp
DC offset 1.35V ***
Frequency 67.7kHz

Change ge-
nerator level
to –50dBm

Spectrumanalyzer
Antenna Switch out-
put, GSM1900
–88 dBm

GSM1800 RX chain
functional

Spectrumanalyzer
4G VCO out
3685.6MHz

∼

–30 dBm (*

Oscilloscope
VANT_3 2.7VV
VANT_1/2 0V

Oscilloscope
LNA_VCC 2.6V
LNA_P 0 V

Oscilloscope
Check HELGA se-
rial interface (burst
mode)

Check HELGA
N500

Check Base-
band

Check  C831,
 L811

* Spectrumanalyzer
reading with 1 kohm
passive probe (right val-
ue add +26 dB)

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
Antenna Switch input
–84 dBm

Spectrumanalyzer
HELGA inputs
GSM1900 
–78 dBm

Check Antenna
switch Z800

Spectrumanalyzer    

RX_SAW_out 
–90 dBm

Check Baseband

Oscilloscope
VR1,3...6  2.7V
Check HELGA serial
interface 
(burst mode)

Check Baseband

Yes

Check HELGA
N500

Yes

Check V802,
C826, Z802,
C829, C8097,
C808

Oscilloscope
VR1,3...6  2.7V
Check HELGA serial
interface 
(burst mode)

Yes

Check Baseband

Synthesiszer trou-
bleshooting

Check HELGA
N500

* ** DC–level of RXI/RXQ in
continuous mode will decrease
slowly.
The original level can be resto-
red by rewriting gain set.