Nokia 7250, 7250i 服务手册

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Check output signal level:

TX signal found ?

Yes

Tune

dead

start TX power level

Tune Tx DAC values

No

PA & ant switch

TX troubleshooting

TX OK

+32...+33dBm @897.4 MHz (GSM900)
+29...+30dBm @1747.8 MHz 
     (GSM1800 &  GSM1900)

  OK ?

Check
all power
levels, 
OK ?

TX power 
levels, 
OK ?

No

Yes

No

Check output signal
on 500 MHZ span
Signal found on 
incorrect frequency ?

Yes

Synthesizer 
troubleshooting

Check with RF probe
signal level on
PA input >=0dBm (*

OK ?

Yes

HELGA
troubleshooting

No

Yes

tuning and check
tuned RAC values:
Highest level~700...900
Lowest level ~190...210
Base levle ~160...190

Major differences ?

Check with oscilloscope:
PA ctrl voltage
>1.5V peak  OK ?

No

troubleshooting

No

Check control loop
components

OK ?

Replace HELGA

*(When 1kOhm passive probe is used,
correct the measurement result by +26dB

Replace 
faulty
component(s)

Yes

Yes

Yes

Yes