U9200 Maintenance Manual
INTERNAL
(2012-06-13)
Huawei Proprietary and Confidential
Copyright © Huawei Technologies Co., Ltd.
Page 47 of 80
Figure 9-3
Large current check process
9.2.2 Low Current (DC Power Supply)
Low current is usually caused by short circuit on the PM chip or system startup failure, which
is due to a faulty main chip or memory chip. The low current ranges from 20 mA to several
hundred mA.
After the phone is connected to a
USB charger or simulated battery,
and the power key is pressed, a
large current is detected.
Is the VBAT circuit
shorted?
N
Y
Are the circuit
elements of the
battery connector
shorted?
Y
Resolder or
replace the
shorted element.
N
Is the U1901,
U1301, U4801, or
U4704 shorted?
N
Y
Resolder or
replace the
shorted element.
Are other circuits,
especially those close to
the connector, shorted?
Check whether the
VPH_PWR circuit is
shorted.
End
Is the current
recovered after the
U1901 is soldered?
Y
N
Check if other circuits,
especially those close to
the connector, are
shorted.