Blu STUDIO 5.0S II, Service Manual

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2.2 RX Circuit
At first, the GSM signals received by the antenna will go through the front model
SAW filter to the MT6166. They are amplified, mixed and modulated into the I/Q carried
by the 100KHz wave, done by the band pass filter, amplifier (controlled gain), filter,
amplifier(controlled gain) and mixer. Then the 4 tracks of I/Q signals are putout the
transiver and sent to the MT6166
The FEM is the ASM, a select switch of RX and TX, GSM and DCS. By this way, the
isolation will be well strengthened and signals will be well protected.
2.3 RF Part examine and Repair -TX
2.3.1 Necessary condition
a. Test condition1 ： voltage=3.8V-4.2V
b. Test condition 2
：
GSM Band
TX mode CH62 Freq=902.4MHz Power Level ： 5
c. Test condition3
：
DCS Band
TX mode CH700 Freq=1747.4MHz Power Level
：
0
c. Test Instrument ： CMU200,Oscillograph, spectrum analyzer
d. Examination of the TX
Make the mainboard into the transmit states by using the special software. In the GSM
band, select the 62
nd
channel, 5
th
power level. In the DCS band, select the 699
th
channel, 0
power level. Then observe whether the current will raise and check the wave by using the
spectrum analyzer or the oscillograph.