Power Output Problems - Lenovo A516 Service Manual

Repair Manual of Lenovo A516 Mobile Phone
Excessive Phase Error
Check the power supply part of PA （U2102） and transceiver
（U2101）
Replace the elements in
solder joint

4.3.4 Power output problems

⚫
Fault: Normally power-on and receive, but when outputting two frequency bands or single
frequency band power, there is no input power or the input power is very low.
⚫
Cause: There are many reasons for no output power or very low power, which may be the
results of faults of Transceiver output part, PA input and output circuit, antenna connector
and antenna switch control signal or power supply circuit. Specific circumstances are:
◼
RF connector（CON2101）
Checking: Whether RF connector CON701 and the test probe of RF test cable are well
connected or the patch is oppositely pasted or the antenna connector is damaged.
Shooting: Replace antenna connector and ensure right direction of patch.
◼
RF power amplifier (PA)
A. Whether the control signal PA_ENABLE（Pin17）of PA is high level (about 2.8V); if it
is low level, there is no output of PA;
B. Check the Pin3 Pin4 of PA power supply part to see whether the power supply voltage
is in the normal range (typically 3.6V ~ 4.2V);
C. Whether the RF input parts of PA(C2101,R2102,C2102,R2105) are in cold solder
joint;
D. Whether the RF output (R2115,C2113,C2131,C2114 )of PA is in cold solder joint;
E. Part circuit of V_ramp control signal of PA(R2111,R21123,C2111): if it is in old solder
joint or in interruption of circuit, PA also has no output power.
◼
Transceiver（U2101）
A. Whether the power supply voltage of Transceiver（U2101） is within normal range;
check the power supply voltage between power supply filtration capacitor and U2101
connection and then check whether the surrounding circuit is in cold solder joint.
B. Whether there is cold solder joint or short circuit in Transceiver （U2101）.
cold
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