Micromax Q427+ User manual

Q427+ L3 Service Manual
1、Technical Specifications
Particular
Remarks
Key Matrix For Flashing
NA
Chipset
MT 6735
Android Version
Android 6.0
Frequency
1GHz Quad core
Network Mode
850MHz/900MHz/1800MHz/1900MHz B1,B3,B7,B20
ROM
16GB
RAM
2GB
Internal SD Card memory
12
Expandable Memory
64G Byte
Factory mode code
press Volume+&Volume-&Power
Good Earpiece volume
32Ω± 15%
Good Loudspeaker volume
8Ω± 5%
Good MIC volume
2.2kΩ± 5%
Good Vibrator volume
30Ω± 5%

Q427+ L3 Service Manual
2：CAUTIONS
I. Flashing & Servicing must be undertaken by qualified personnel only.
II. Ensure all work is carried out at an anti-static workstation and that an anti-static wrist strap is worn.
III. Use only approved Tools & components as specified in the parts list.
IV. Ensure all components, modules, screws, and insulators are correctly re-fitted after servicing and
alignment
V. Ensure all cables and wires are repositioned correctly if Handset disassembled
VI. Electrostatic discharge can easily damage the sensitive components of electronic products.
Therefore, Service Centre must Adhere the precautions which mentioned above.
3. L3 Service Manual
J1601
Earphone
Connector
U601
Power chip
U1703
Proximity
Sensor
U1200
RF sw
J1600
Receiver
Connect
or
J1501
Main camera
Connector
U1300
GPS/WIFI/F
M/BT chip
U401
Flash
J1200
RF connector
U800
RF chip
U900
3G/4G PA
U400
CPU
Y1300
Crystal
D1700
charge
indicator
U1401
Backlight
Drive
Z1101/Z1102
RF filter

Q427+ L3 Service Manual
J1400
LCD
connector
U1706
Gyro sensor
J1804
FPC
connect
J1801
SIM
connector
J1402
TP connector
J1602
MIC
J1802
Battery
connect
J1803
T-FLASH
connector
D1500
Flashlight
J1700
Key
connect
E1101
RF
connector
E1301
Wifi/BT ANT
J1500
Camera
Connector
J1800
SIM
connecto
r

Q427+ L3 Service Manual
1. Unable to load Software:
Solution:
First check the computer can recognize the device or not, if not, Re-load it.
Then check the USB port to master control circuit is normal or not.：format the flash and upgrade again if fail
in the Proceed of downloading.
Use a new data cable
Check the I/O connector soldering quality, if not, Re-sold it or change it.
Check the Main FPC Assembly quality, if not, Re-Assembly it or change it.
Check the FPC connector soldering quality, if not, Re-sold it or change it.
Check the CPU work normally or not. Re-Solder the CPU or change it
I/O
connector
FPC
connector
Main FPC

Q427+ L3 Service Manual
2. No power on
Solution:
Flash the handset with latest SW
Check the battery have capacity or not ,if not ,Change it
Charging with transferred to 4.0 V dc power supply to the mainboard on battery Re-soldering ,check
The mainboard work current, the normal starting current will be from 100 ma jump to light screen
Enter boot LOGO 400 ma to completely started around 500 ma, if the current not right then check
Whether has short circuit or open circuit phenomenon or not.
Check the Power IC work normally or not ,Re-Solder it or change it
The output voltage normally or not
Check the 26M crystal work normally or not ,Re-Solder it or change it
Check the CPU work normally or not, Re-Solder CPU or change it
26M
crystal
CPU
Power
ic

Q427+ L3 Service Manual

Q427+ L3 Service Manual
3. Not charging:
Solution:
Flash the handset with latest SW
Plug in the charger to check whether the machine has a charging icon, if don’t have, then check the
5V power pin of USB port connect the mainboard or not
Check the voltage of battery when charging If it reaches 4.2V, has shown in front of the
Transmission, now maybe is the battery bad so that no charging.
Check the I/O connector work well or not ,if not , Re-Solder or change it
Check the Main FPC Assembly Quality , if not ,Re-Assembly it or change it.
Check the FPC connector soldering quality , if not ,Re-sold it or change it.
Check the charging switch work well or not ,if not , Re-Solder or change it
Check the Power IC work normally or not, Re-Solder CPU or change it
Check the CPU work normally or not. Re-Solder the CPU or change it
I/O
connector
FPC
connector
Main FPC
Power IC
Charging
switch

Q427+ L3 Service Manual

Q427+ L3 Service Manual
4. LCD / Display problem:
Solution:
Flash the handset with latest SW
Check the connect ribbon cable saddle normally or not , Re-assembly LCD.
Check the LCD connector work normally or not, Re-Solder LCD connector or change it
Check the CPU work normally or not, Re-Solder CPU or change it
.
CPU
LCD
connector

Q427+ L3 Service Manual
5. Touch panel is not working N/A
Flash the handset with latest SW
Check the connect ribbon cable saddle normally or not, Re-assembly TP.
Check the TP connector work normally or not, Re-Solder TP connector or change it
Check the CPU work normally or not, Re-Solder CPU or change it
TP connector
CPU

Q427+ L3 Service Manual
6. LCD backlight not on or dark
Solution:
Flash the handset with latest SW
Check the connect ribbon cable saddle normally or not , Re-assembly LCD.
Check the LCD connector work normally or not, Re-Solder LCD connector or change it
Check the Backlight IC work normally or not, Re-Solder Backlight IC or change it
Check the CPU work normally or not, Re-Solder CPU or change it
Backlight
IC
LCD
connector

Q427+ L3 Service Manual

Q427+ L3 Service Manual
7. SIM not detecting:
Solution:
Flash the handset with latest SW
Check the SIM card socket is obviously damaged, if yes, Replace the SIM card socket
Check the ground impedance of each pin of the SIM card socket(except the ground pin)is low(lower than
grade ),if yes, Replace the resistor of the corresponding pin;
Check if the series resistors on each network of the SIM card have pseudo soldering ,if yes, Carry out repair
soldering of the series resistors on each signal line;
Check the Power IC normally or not, then Re-Solder Power IC or change it.
Check the CPU normally or not, then Re-Solder CPU or change it.
SIM
Connector
CPU
Power IC

Q427+ L3 Service Manual

Q427+ L3 Service Manual
8. SD card not detecting:
Solution:
Flash the handset with latest SW
Check if the TF card is obviously damaged, if yes, Re-Solder TF connector or change it
Check if the ground impedance of each pin of the TF card socket(except the ground pin)is low(lower than
grade ),if yes, Replace the resistor of the corresponding pin;
Check if the series resistors on each network of the TF card have pseudo soldering ,if yes, Carry out repair
soldering of the series resistors on each signal line;
Check the Power IC normally or not, then Re-Solder Power IC or change it.
Check the CPU normally or not, then Re-Solder CPU or change it.
TF
connector
Power IC
CPU

Q427+ L3 Service Manual

Q427+ L3 Service Manual
9. Front camera is not working:
Solution:
Flash the handset with latest SW
Check if the Camera is obviously damaged, if yes, Replace the Camera ;
Check if the ground impedance of each pin of the Camera connector (except the ground pin)is low(lower than
grade ),if yes, Replace the resistor of the corresponding pin;
Check if the series resistors on each network of the Camera connector have pseudo soldering ,if yes, Carry out
repair soldering of the series resistors on each signal line;
Check the CPU normally or not, then Re-Solder CPU or change it.
Camera
connector
CPU

Q427+ L3 Service Manual
10. Rear camera is not working:
Solution:
Flash the handset with latest SW
Check if the Camera is obviously damaged, if yes, Replace the Camera ;
Check if the ground impedance of each pin of the Camera connector (except the ground pin)is low(lower than
grade ),if yes, Replace the resistor of the corresponding pin;
Check if the series resistors on each network of the Camera connector have pseudo soldering ,if yes, Carry out
repair soldering of the series resistors on each signal line;
Check the CPU normally or not, then Re-Solder CPU or change it.
Camera
connector
CPU

Q427+ L3 Service Manual
11. MIC no sound:
Solution:
Flash the handset with latest SW
Check the MIC bad or not. then Re-Solder MIC or change it
Check the connection of main board and vice board normally or not.
Check Earphone connector also , If Earphone connector got shorted : MIC & Receiver will not work
Check the MIC work normally or not , Re-Solder the MIC or change it.
Check the Main FPC Assembly Quality , if not ,Re-Assembly it or change it.
Check the FPC connector soldering Quality , if not ,Re-sold it or change it.
Check the power IC work normally or not. Re-Solder the power IC or change it
Check the CPU work normally or not. Re-Solder the CPU or change it
MIC
Main FPC

Q427+ L3 Service Manual
FPC
connector
CPU
Power IC