LG LG500, Service Manual

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5.2.9 TX POWER Trouble
5. Data Kit & Test Method
Setup Test with LAPUTA
GSM : 62CH, DAC value 600
DCS : 700CH, DAC value 700
Check or Replace U803 and
circumference circuit
Check or Replace U401 and
circumference circuit
Check or Replace U402
Check or Replace U403 and
circumference circuit
Check or Replace resistors
between U430 and U302
The output voltage level
of IC300(GSM:PIN9, DCS:PIN8) is about 2V
(normally it’s about 1.5V)
The PA_ON signal level
of IC300(PIN7)is Hight(over 2.7V)
The PA_level signal voltage
of IC300(PIN6) is over 1.0V
The Tx IQ Signal
level of U402(PIN39~42) is from
DC1.35V to 0.47V P-P
swing signal
RF signal of U401(PIN10)
is over-5dBm. (GSM at 1229.4MHz,
DCS at 1566.8MHz)
The Voltage level of
U403(PIN7) is lower than 0.2V(GSM)
and hight than 2.7V(DCS)
Modulated Tx signal of
U403(GSM:pin6, DCS:pin10)
about 8dBm (GSM902.4MHz,
DCS 1747.8MHz)
Modulated Tx signal
of U302(GSM:pin12, DCS pin16) is
about 0dBm(GSM902.4MHz,
DCS 1747.8MHz)
Amplified Tx signal of
U302(GSM:PIN4, DCS:PIN8)
is about 30dBm
Input power of SW300
(GSM : PIN7, DCS:PIN13)
is about 30dBm
Check calibration data
and Replace SW300
Check or change N300
and circumference circuit
Replace IC300
Replace U302
Replace U801
Replace U803
NO
NO
NO
NO
NO
NO
NO
NO
NO
NO
YES
YES
YES
YES
YES
YES
YES
YES
YES
YES
NOTE : To get to the Test mode,
press 2945
→
#, then hold
down * key.
U801 : ULYSSE
U803 : OMEGA
U302 : PAM
U401 : PLL
U402 : TRF6053
U403 : TXVCO
SW300 : Antenna switch
IC300 : APC IC
N300 : Directional coupler