U9500 Maintenance Guide
9 Troubleshooting
Issue 1.2 (2012-6-30)
Huawei Proprietary and Confidential
Copyright © Huawei Technologies Co., Ltd.
40
Subsystem Module
Unit
Function
UVLO
Low-voltage power-off function. When the input voltage is
lower than the threshold for a certain period, the phone
powers off.
WDT reset
Supports WDT counter overflow reset function.
Over-temperature
protection
When the on-chip junction temperature is over 150°C, the
phone powers off.
Internal driver
circuits
Provides four LED drivers, one oscillator driver, and one
speaker driver.
Interrupt
management
There is an embedded interrupt manager to process the
related interrupt signals.
USB driver
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.
For details about the conceptual diagram and component layout for maintenance, see the
following compressed files:
HD1FRONTM.rar
U9500_Bottom.rar
U9500_TOP.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 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.
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.
