Micromax Q427+ User manual

Q427+ L2 Service Manual
1：Technical Specifications
Particular
Remarks
Key Matrix For Flashing
NA
Chipset
MT6735P
Android Version
Android 6.0
Frequency
1.3GHz
Network Mode
2G: 850MHz/900MHz/1800MHz/1900MHz
3G: B1 B8
Data Segment
GPRS, EDGE, HSPA+ 21Mbps, FDD-LTE, TDD-LTE
Rom
16G
RAM
2G
Internal SD Card memory
12G
Expandable Memory
64G
Factory mode code
Press vol+/ Vol-/ power key at the same time
Good Earpiece volume
32Ω± 15%
Good Loudspeaker volume
8Ω± 5%
Good Mic volume
2.2kΩ± 5%
Good Vibrator volume
30Ω± 5%

Q427+ L2 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、service Details
Main
camera
Earphone
connector
Vibrator
Charge
connector
Front
camera
SIM
connector
TP
Connetor
SIM
connector
Battery
connector
RF coaxial
line
RF
Antenna
Main
FPC
LCD
connector
GPS
ANT
SPK
RFANT
T-Flash
connecto
r
Volume
key FPC
Battery
Wifi /BT
ANT
Fingerprint
FPC

Q427+ L2 Service Manual
1. Does not power on
S.NO
Possible Cause
Validation steps
Action
1
Shorting
Check shorting with Multi meter
Replace PCB if found
faulty
2
Battery
a) Clean the 3 or 4 golden color
point(its terminals)on the battery
b) Check voltage with Multi meter
Value must be 3.7V DC or above
Replace if found faulty
3
Battery
Connector
a) Check battery connector
b) Keep Multi meter on 20V DC and
check value must be 1.5 to 3.5V DC
Re-solder/Replace if
found faulty
4
SW failure
Flashing with latest software
Flashing
5
Power on Key
Key failure
Re-solder/Replace if
found faulty
6
PCB
Suspected PCB faulty
Refer L3 repair
Side Key
Battery
connector

Q427+ L2 Service Manual
2：Display issue/No display
S.NO
Possible Cause
Validation steps
Action
1
No display
SWissue
Flash the handset with latest SW
LCD issue
Re-assembly LCD/Replace it
PCBA issue
Re-assembly PCBA/Replace it
PCBA issue
Re-Solder the LCD connector or change it
2
Colored screen
LCD issue
Re-assembly LCD/Replace it
3
Dark screen
LCD issue
Re-assembly LCD/Replace it
SWissue
Flash the handset with latest SW
LCD backlight circuit issue
Refer L3 repair
LCD backlight is set
too low by person
Reset the value of backlight
LCD
connector
LCD

Q427+ L2 Service Manual
3：Touch panel
S.NO
Possible Cause
Validation steps
Action
1
TP not working
SW Issue
Flash the handset with latest SW
TP issue
Re-assembly TP/Replace it
PCBA issue
Refer to L3 repair
PCBA issue
Re-Solder the TP connector or change it
2
TP not working proper
TP issue
Re-assembly TP/Replace it
PCBA issue
Refer to L3 repair
TP
TP
connector

Q427+ L2 Service Manual
4：Proximity Sensor
S.NO
Possible Cause
Validation steps
Action
1
Proximity sensor fail
SW Issue
Flash the handset with latest SW
Sensor holder is not
assembled well
Re-assemble the sensor holder
PCBA issue
Change PCBA
5：G-sensor
S.NO
Possible Cause
Validation steps
Action
1
G-sensor is not working
SW Issue
Flash the handset with latest SW
Set problem
Reset mobile
PCBA issue
Change PCBA
Proximity
sensor
G-sensor

Q427+ L2 Service Manual
6：Keys
S.NO
Possible Cause
Validation steps
Action
1
Key is not response
Key is fail
Change Key
SW Issue
Flash the handset with latest SW
2
The feeling of pressing
key is bad
Key soldering Quality
Solder Key again
Some dust with dome
Clean it
Key is not assembled well
Re-assemble
Side Key

Q427+ L2 Service Manual
7：Charging
S.NO
Possible Cause
Validation steps
Action
1
Cannot charge into
Adapter is fail
Change adapter
Cable is fail
Change Cable
Battery is issue
Charging or Change it
Main FPC issue
Re-assembly or Change it
I/O connector is fail
Re-Solder or Change it
2
Have charging icon, but
not charged
SW Issue
Flash the handset with latest SW
PCBA fail
Change PCBA
Battery fail
Change battery
Battery connector issue
Change battery connector
Main FPC
Battery
connector
Adapt
er
I/O
connector
USB
Cable

Q427+ L2 Service Manual
8：USB
S.NO
Possible Cause
Validation steps
Action
1
Cannot connect to PC
USB cable is fail
Change USB cable
I/O connector fail
Re-Solder or Change it
Main FPC issue
Re-assembly or Change it
PCBA fail
Change PCBA
USB
Cable
I/O
connector
Main
FPC

Q427+ L2 Service Manual
9：Front Camera
S.NO
Possible Cause
Validation steps
Action
1
Colored screen when
open front camera
Camera is issue
Re-assembly camera or Change it
PCBA fail
Change PCBA
2
Cannot turn on Rear
camera
SW issue
Flash the handset with latest SW
Camera issue
Re-assembly or Change it
Camera issue
Re-Solder or Change Camera connector
PCBA fail
Change PCBA
Front
camera

Q427+ L2 Service Manual
10：Rear Camera
S.NO
Possible Cause
Validation steps
Action
1
Colored screen when
open front camera
Camera is fail
Re-assembly or Change it
PCBA fail
Change PCBA
2
Cannot turn on Rear
camera
SW issue
Flash the handset with latest SW
Camera fail
Re-assembly or Change it
Camera issue
Re-Solder or Change Camera connector
PCBA fail
Change PCBA
11：Playing Video
S.NO
Possible Cause
Validation steps
Action
1
Hang often
SW issue
Flash the handset with latest SW
Flash poor soldering
Refer L3 Repair
CPU poor soldering
Refer L3 Repair
Main
camera
Flash
CPU

Q427+ L2 Service Manual
12：Vibrator
S.NO
Possible Cause
Validation steps
Action
1
Vibrating is not properly
Vibrate assemble issue
Re assemble it
SW issue
Flash the handset with latest SW
Main FPC issue
Re-assembly Main FPC or change it.
2
NO vibrate
Soldering issue
Re soldering it
PCBA issue
Re soldering FPC connector or change it
Vibrate SUB issue
Re-assembly Vibrate SUB pcba
PCBA issue
Refer to L3 service
3
Vibrate weakly
Vibrate issue
Change it
13：WiFi/BT
S.NO
Possible Cause
Validation steps
Action
1
WI-FI not working
Set wifi turn off as default
Reset wifi to turn on wifi
SW issue
Flash the handset with latest SW
WiFi/BT antenna
Re-assembly WiFi/BT antenna or
change it.
PCBA issue
Change PCBA
Main FPC
Main FPC
connector
Vibrate
SUB
PCBA
WiFi/BT
antenna
Antenna
Slot

Q427+ L2 Service Manual
14：RF Network
S.NO
Possible Cause
Validation steps
Action
1
RF Network cannot
searchable
SW issue
Flash the handset with latest SW
RF antenna issue
Re-assemble or Change it
SIM socket is fail
Re-Solder or Change it
Some dust with RF Slot
Clean it
RF Coaxial line issue
Re-assemble or Change it
RF connector issue
Re-Solder or Change it
PCBA fail
Change PCBA
RF antenna
Slot
RF Coaxial
line
RF
antenna
RF
connector
SIM
connector

Q427+ L2 Service Manual
15：FM
S.NO
Possible Cause
Validation steps
Action
1
Cannot turn on FM
SW issue
Flash the handset with latest SW
Earphone is fail
Change Earphone
FM antenna fail
Re- Solder or Change earphone connector
PCBA fail
Change PCBA
Earphon
Ee
Earphone
connector

Q427+ L2 Service Manual
16: Receiver
S.NO
Possible Cause
Validation steps
Action
1
Noise/crack
Dust with receiver
Clean it
Receiver issue
Re-assemble or Change it
2
Noise/volume low
SW issue
Flash the handset with latest SW
Receiver is set too low by
person
Reset the value of volume
PCBA issue
Re-assemble or Change it
Receiver
Receiver
slot

Q427+ L2 Service Manual
17：Earphone
S.NO
Possible Cause
Validation steps
Action
1
Not working / from
earphone
SW issue
Upgrade the handset with latest SW
Earphone is fail
Change Earphone
PCBA issue
Refer to L3 service
Earphone connector
having poor soldering
Re-Solder or Change it
Earphon
e
Earphone
connector

Q427+ L2 Service Manual
18：MIC
S.NO
Possible Cause
Validation steps
Action
1
Noise with uplink side
Some dust with MIC
Clean it
MIC issue
Re-assemble or Change Main FPC
MIC issue
Re- Solder or Change Main FPC
connector
PCBA issue
Refer to L3 repair
2
Volume low
soldering issue
Re-Solder or Change it
Volume is set too low by person
Reset the value of volume
PCBA issue
Refer to L3 repair
3
No recording
MIC issue
Re-Solder or Change it
SW issue
Flash the handset with latest SW
PCBA issue
Refer to L3 repair
MIC
FPC
connector
Main FPC

Q427+ L2 Service Manual
19: GPS
S.NO
Possible Cause
Validation steps
Action
1
GPS not connecting
SW issue
Flash the handset with latest SW
Set GPS turn off as default
Reset GPS to turn on GPS
GPS antenna issue
Re-assemble or Change GPS antenna
PCBA issue
Refer to L3 service
GPS
antenna
Antenna
Slot

Q427+ L2 Service Manual
20: Speaker
S.NO
Possible Cause
Validation steps
Action
1
Noise/crack
Speaker with dust
Clean speaker
Speaker foam issue
Re-assemble or Change SPK
Speaker issue
Change speaker
2
No volume
Assemble issue
Assemble again
SW issue
Flash the handset with latest SW
Speaker issue
Re-assemble or Change Main FPC
Speaker issue
Re-Solder or Change Main FPC
connector
Speaker issue
Re-Solder or Change SPK FPC
3
Low volume
Assemble issue
Assemble again
Volume is set too low by
person
Reset the value of volume
Speaker issue
Change it
Audio PA issue
Refer to L3 repair
SPK FPC
FPC
connector
Main FPC
SPK

Q427+ L2 Service Manual
21：Battery
S.NO
Possible Cause
Validation steps
Action
1
Show charging but it
is not charged
Battery issue
Change battery
Charging connector issue
Re-Solder or Change it
2
No charging
PCBA issue
Re-assemble or Change PCBA
PCBA issue
Refer to L3 repair
3
Cannot charge fully
Some dust with Battery golden color
point
Clean golden color point
PCBA issue
Change PCBA
battery connector issue
Change battery connector
Thanks
For any Query or suggestion, Please write to [e-mail]
Battery
Battery
connector