Nokia 7250, 7250i Service Manual

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No

No

Yes

Yes

No

No

Yes

No

Yes

No

Yes

Yes

Yes

Apply –90dBm
942.46771MHz signal
from generator to anten-
na connector

Oscilloscope at RX_I
Signal 700mVpp
DC offset 1.35V***
Frequency 67.7kHz

No

Change ge-
nerator level
to –50dBm

Spectrumanalyzer
Antenna Switch
outputs, GSM900
–88 dBm

Spectrumanalyzer
Antenna Switch
input
–84 dBm

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

Synthesiszer trou-
bleshooting

Spectrumanalyzer
4G VCO out
3769.6MHz

∼

–30 dBm (*

Oscilloscope
VANT_1...3 0V

Oscilloscope  :
Check HELGA
serial interface
(burst mode)

Check HELGA
N500

Check Base-
band

* Spectrumanalyzer
reading with 1 kohm
passive probe (right val-
ue add +34 dB)

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.

900RX chain
functional

Check C831,

L811

Check Antenna
switch 
Z800

Spectrumanalyzer
HELGA inputs
GSM900
–89 dBm

Check L809
L810

Check Base-
band

No

Yes

Yes

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.