LG H990ds - GSM Tx Signal Path (Bands 850;900;1800;1900)

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reserved. Only training and service purposes
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3. TROUBLE SHOOTING
Checking Flow Image
Checking Tx signal path(GSM850/900/1800/1900)
Check TP1
+VBAT OK?
START
The Problem may be Other part
Check QFE2101 Logic part
YES
NO
YES
The Problem may be Other part
Check QFE2101 Logic part
NO
Check TP2
3.2V≤TP2≤4.2V?
Check
TP3/4
If GSM850/900 Over 31dBm?
If DCS/PCS Over
28dBm?
NO
Check next step
Check component
above RF signal path
YES
Check
TP5/6
If GSM850/900 Over -5dBm?
If DCS/PCS Over
-5dBm?
YES
Check U1301 soldering
NO
Check
Transceiver
physical damage
or soldering
condition
OK
NOT GOOD
Replace U1400
3.7.2 GSM PART – GSM850/900/1800/1900 Tx
TP2(+VPWR_BOOST_BYPASS_RF)
U1601
U1301
(MMPA)
TP5(GSM850/900 Tx)
TP3(GSM850/900 Tx)
TP6(GSM1800/1900 Tx)
TP4(GSM1800/1900 Tx)
TP1(+VBAT)
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