Lenovo i909 Podręcznik konserwacji - Strona 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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