Power-On Failure; Large Current (Dc Power Supply) - Huawei U9200 Maintenance Manual

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9.2 Power-On Failure

If a phone cannot be powered on, you should inspect the phone to locate the fault. Possible

causes of power-on failure are listed as follows:

Detailed fault location methods are described as follows:

To locate the fault on the main board, connect the phone to a USB charger, and check the

current.

There are three scenarios: large current, low current, and no current. The following sections

provide detailed analysis on the three scenarios.

Large current is usually caused by short circuit. The current reaches 500 mA or above (the

over-current protection value of a USB charger) when using DC power supply. For U9200,

large current is usually caused by ground short circuit of VBAT and VPH_PWR.

(2012-06-13)

U9200 Maintenance Manual

The battery is damaged because of unknown reasons, resulting in no output voltage, poor

contact between connectors, or low output voltage, in which case the phone enters a low

power consumption state once being powered on.

The main board is faulty.

The LCD is damaged which seems that the phone cannot be powered on.

The FPC of the power key is faulty, resulting in no response when you press the power

key.

Press the power key, and listen whether the motor rotates. If the motor rotates, the LCD

is damaged. Change the LCD, and check whether the phone can be powered on.

If the motor does not rotate, connect the phone to a USB charger, and if the phone enters

the charging state, the FPC of the power key or the battery is faulty.

If the phone does not enter the charging state, the main board is faulty or the battery is

faulty. In this case, disassemble the phone to inspect whether the battery and the power

key are in good condition. If they are, the power-on failure is caused by a faulty main

board.

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