Failure And Handling Process; Power-On Failure - Huawei U9500 Maintenance Manual

U9500 Maintenance Guide
Subsystem Module
For details about the conceptual diagram and component layout for maintenance, see the
following compressed files:
HD1FRONTM.rar

9.2 Failure and Handling Process

9.2.1 Power-On Failure

Cause
If a phone cannot be powered on, inspect the phone to locate the fault. Possible causes for the
power-on failure are listed as follows:



The power-key FPC is faulty, resulting in no response when you press the Power key.
Damage or short-circuit on several components may cause the power-on failure. 0 and Figure
9-5 show these components.
Issue 1.2 (2012-6-30)
Unit
UVLO
WDT reset
Over-temperature
protection
Internal driver
circuits
Interrupt
management
USB driver
U9500_Bottom.rar
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
voltage state once being powered on.
The PCBA is faulty.
The LCD is damaged and nothing displays on the screen. It seems that the phone cannot
be powered on.
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Function
Low-voltage power-off function. When the input voltage is
lower than the threshold for a certain period, the phone
powers off.
Supports WDT counter overflow reset function.
When the on-chip junction temperature is over 150° C, the
phone powers off.
Provides four LED drivers, one oscillator driver, and one
speaker driver.
There is an embedded interrupt manager to process the
related interrupt signals.
There is an embedded OTG USB driver supporting USB
2.0 HS. The interface is of /B type. The software does not
support OTG function now.
U9500_TOP.rar
9 Troubleshooting
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