Blu VIVO 4.8, Service Manual

Page: 15 / 24

Page 15 of 24
2.2.4 Baseband Fault issues
Maintenance process of the download failure Issues:
Download Fail
Check to see if it is caused by other
factors such as: configuration, download
cable, power supply, software and PC
Exclude the reason of
download failure
caused by other factors
Yes
Check to see if the serial ports between
pc and cell phone is smooth
Check if the system
connector is poor
soldered or damaged.
NO
NO
Check the resistance,
capacitance and the
EDC devices between
the system connector
and the CPU.
NO
Connect the download cable then
observe the Ammeter to see if it
shows high current
（
The normal
current generally about 30mA
）
Yes
Quickly disconnect the
connection, and gently
touch the chip to see if it is
hot. If not, then focus point
using the multi-meter to
measure the short circuit.
Yes
Check the power manager and open the
LDO to see if the voltage supply is
normal and whether there is power
supply circuit open.
Little or no current
Check VCORE
、
VDD
、
VADD
、
VTCXO
、
VRTC
、
VMEM
、
Measure the clock signal of
26MHZ
、
32KHZ.
Current normal but download fail
Check CPU and NAND FLASH
、
SDRAM to
see if they are OK and the LDO is normal.