LG H990ds Service Manual page 23

3.5.3 LTE PART – B1/B2/B3/B4/B5/B8/B12/B17/B20/B26/B28/B39 Tx
Checking Tx signal path(LTE B1/B2/B3/B4/B5/B8/B12/B17/B20/B26/B28/B34/B39 Tx)
START
Check TP1/TP3
+VPA0 OK?
YES
Check TP2
3.2V≤TP2≤4.2V?
YES
Check TP4~13
If LTE of All band
Over 22dBm?
NO
Check TP4~13
If LTE of All band
Over 10dBm?
NO
Check
Transceiver
physical damage
or soldering
condition
OK
Check next step
LGE Internal Use Only
The Problem may be
other part and
Check QFE2101 Logic part
NO
The Problem may be
other part and
NO
Check QFE2101 Logic part
Check component
above RF signal path
YES
and FEMid Block
Replace U1301
YES
NOT GOOD
Replace U1400
TP2(+VPWR_BOOST_BYPASS_RF)
U1601
TP6(B3/4 Tx)
TP4(B1 Tx)
U1301
(MMPA)
TP3(+VPA0)
TP12(B28B Tx)
23
3. TROUBLE SHOOTING
Image
TP1(+VPA0)
TP13(B39 Tx)
BOTTOM
TP5(B2 Tx)
TP7(B5/26 Tx)
TP10(B20 Tx)
TP8(B8 Tx)
TP9(B12/17 Tx)
TP11(B28A Tx)
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