Lenovo i909 Maintenance Manual - Page 26

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I908 Mobile Phone Maintenance Manual

Cause of the Problem: The capacitors of the PA and transceiver power supply sections have

faulty soldering points or are short circuited with other resistors.

Solution:

4.3.4 Power output problems

Problem: The unit can be turned on and receipt is normal, however, there is no power

output, or power output is low when dual or single power frequencies are output

Causes: Many causes can lead to no or little output power, such as signal failures or circuit

troubles with the transceiver output section, PA I/O circuit, antenna connector and antenna

switch control. Cause of the Problem:

Antenna Connector (U2105)

Check: Check the connection between the antenna connector U2105 and RF test probes.

Alternatively, check whether or not the chip has been attached in the wrong direction or if the

antenna connector is damaged.

Solution: Replace the antenna connector and make sure that the chip is attached in the

right direction.

Antenna Switch (U2104)

Check: Check for pseudo soldering at the antenna switch U2104 and its peripheral circuits,

pay special attention to the magnetic beads L2114 and L2104 on the pins (Pin2, Pin10) of the

antenna switch control signal.

Solution: Replace pseudo soldering assembly (assemblies)

RF Power Amplifier (PA)

Check whether or not the control signal of the PA (PA_EN (pin3)) is at a high voltage, i.e.

around 2.8V;If it is at a low voltage, then the PA has no output; Check the

series-wound 1K ohm resistor R2102 for possible pseudo soldering or disconnection

again.

Check the power supply of PA at Pin4 to see whether the voltage is within normal

range (normally 3.6V~4.2V);

Check RF input parts of PA, such as Z2103, L2106 and L2107 for possible pseudo

soldering;

Phase Error overruns

Check the power supply circuitry of

PA (U2102) and the Transceiver

Replace

elements

ith

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