Micromax X771 Service Manual

Particular

Remarks

Key Matrix For Flashing

NA

Chipset

SC6531E

Android Version

NA

Frequency

GSM:850/900/1800/1900

Network Mode

Dual SIM:GSM

ROM

32Mb

RAM

32Mb

Internal SD Card memory

NA

Expandable Memory

32 GB

Factory mode code

*#629#

Model X771 L3 Service Manual

2. CAUTIONS

1. Technical Specifications :

Please fill below information in Remarks, Below given remarks are for reference only

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.

J400 earphone connector
Failure caused by damage:
Earphone failure, FM failure

J100 antenna bonding pad
Failure caused by damage:
Weak BT signal

J800/J802 SIM1/SIM2 card
socket
Failure caused by damage:
Failure to identify GSM/

U600 charge IC
Failure caused by damage:
Failure to No indication during
charging

ANT1/ANT2 GSM PAD
Failure caused by
damage: GSM failure

U0101 GSM PA chip Failure caused
by damage:RF failure

U300 communication processor
Failure caused by damage:
Power-on failure

SPK speaker
Failure caused by
damage: No sound from
speaker

CAM pad
Failure caused by
damage:CAM failure

J602 Bat connector
Failure caused by
damage:
Power-on failure

LCD LCD pad
Failure caused by damage:
Display backlight failure

D700/D701/D702/D703/D704/D705
Keypad backlight
Failure caused by damage:
Keypad backlight failure

LED pad Failure caused
by damage: LED torch
failure

USB Connector Failure
caused by damage: No
port, no charging

Model X771 L3 Service Manual

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.

Basic Structure of the Mobile Phone

PCBA Diagrams of A81 Mainboard

GOLD_MIC,MIC pad
Failure caused by
damage:
No sound when voice is
transmitted via local MIC;

Model X771 L3 Service Manual

3. L3 Level trouble shooting

Please add trouble shooting/ Repairing steps against below given symptoms
Images must paste against every suggested troubleshooting hint

1) Doesn’t Power On

Y200

U300

J602

Model X771 L3 Service Manual

Solution

A- There is no current when the Power Key is pressed; check J602 to see if there is false soldering,

pseudo soldering, if yes, Carry out Resoldering or replacement;

B- When the Power Key is pressed, and the current stays within 10~15mA, if yes, Upgrade the

software version;

C- There is current when the Power Key is pressed; the current changes to 0~5mA when the key is

loosened, if yes, The problem is caused by pseudo soldering or damage of 26M crustal(Y200);
carry out repair soldering or replacement of the crystal. Or, it is caused by pseudo soldering or
damage of CPU;

D- There is heavy current when the Power Key is pressed, if yes, Find the hot point, and replace the

corresponding material CPU(U300) are damaged in most cases.

2) Restart / Hang
Solution: Refer same to Power failure issue.

3) LCD

LCD

U300

Model X771 L3 Service Manual

Solution:

A- Exchange the front shell to judge if the LCD itself is abnormal, if yes, Replace the LCD;
B- Replace the CPU(U300)

4) Touchpad
NA

5) Proximity Sensor
NA

6) Accelerometer
NA

7) Keypad

Model X771 L3 Service Manual

Solution:

A- The common breakdown mainly does not work for the pressed key, the pressed key expiration. May defer to the

schematic diagram to examine whether by short circuit, abruption phenomenon. Or examined whether
underneath Dome has the foreign matter.

8) Charging
Solution:

A- Check if the charging IC U600 is abnormal, if yes, Carry out repair soldering or replacement;
B- Check if the resistors R601 are abnormal, if yes, Carry out repair soldering or replacement;

U300
R601

U600

Model X771 L3 Service Manual

C- Replace the U300

9) USB
Solution:

J603

U600

R601
U300

Model X771 L3 Service Manual

A- Check if the connector J603 is damaged or pseudo soldering, if yes, Carry out repair soldering or

replacement of the material

B- Check if the charging IC U600/R601 is abnormally soldered or damaged, if yes, Carry out repair

soldering or replacement.

C- Replace U300

10) Main Camera

J500

Model X771 L3 Service Manual

Solution:

A- Check if the camera is properly installed, if yes, Reinstall it;
B- Exchange the camera to see if the problem is solved, if yes, The problem is caused by the

camera itself; replace it;

11) Front Camera
NA

RF_
ANT

Model X771 L3 Service Manual

12) Flash Light
NA

13) Vibrator

NA

14) Network
Solution:

A- Test the conduction power to see if it normal; if normal, test the circuit between the RF test

pad and the antenna to see if it is normal; or else, see the analysis of“abnormality of
conduction power”.

B- Test the circuit between the RF test pad and the antenna to see if it is normal are shown in the

following chart;

C- Check if the contact between the antenna and the antenna spring clip is normal. Deformation

of the antenna spring clip, which will affect coupling of RF signal, further resulting in low
coupling power. This problem can be solved by replacing the damaged component.

D- Damage of component material in the RF circuit, which can be solved by replacing the

material;

E- Pseudo soldering of components, which can be solved by repair soldering;
F- Direction error or position shift of components due to surface mounting, which can be solved

by Properly soldering the components;

G- Power abnormality caused by abnormal calibration, which can be solved by using proper

Calibration software configuration and instrument.

The repairman can check item by item according to the signal trend in the diagram, so as to

Determine the failure position.

BT
PAD

Model X771 L3 Service Manual

15) 3G-LTE not working
NA

16) WI-FI
NA

17) Bluetooth
Solution:

A- Exchange the BT ANT to see if the problem is solved, if yes, It is the problem of the BT ANT
B- The repairman can check item by item according to the signal trend in the diagram, so as to Determine

the failure position.

Earphone
jack

Model X771 L3 Service Manual

18) FM / Radio
Solution:

A- Exchange the earphone to see if the problem is solved, if yes, It is the problem of the earphone.
B- Exchange the earphone jack to see if the problem is solved, if yes, It is the problem of the earphone

jack.

C- The repairman can check item by item according to the signal trend in the diagram, so as to Determine

the failure position.

Earphone
jack

U300

L402

L401

Model X771 L3 Service Manual

19) Heating
Please refer same with Power-on failure.

20) Ear Phone
Solution:

A- Visually inspect the earphone jack to see if there is any abnormality, if yes, Replace the earphone jack
B- Check if L401,L402have pseudo soldering, if yes, Carry out repair soldering;
C- Replace U300

21) Outgoing Audio / MIC
Solution:

A- Exchange the MIC to see if the problem is solved, if yes, It is the problem of the MIC
B- Pseudo soldering of C6009,C6017,R6003,R6000,R6007 and R6008 on the PCBA;
C- Problem of U1000

R402

R401

R400

U300

R403

C400

C404

Model X771 L3 Service Manual

22) Incoming Audio / Earpiece
Solution:

A- Visually inspect the earphone jack to see if it is abnormal, if yes, Replace the earphone jack;
B- Check if L401 L402 L400 have pseudo soldering, if yes, Carry out repair soldering;

Earphone
jack

L400

U300

L402

L403

L401

U400

U401

Model X771 L3 Service Manual

23) Speaker

Solution:

A- Exchange the speaker to see if the problem is solved, if yes, It is the problem of the speaker;
B- Check if U400,U401 have pseudo soldering or damage, if yes, Replace U400/U401
C- Replace U300

U300

J801

Model X771 L3 Service Manual

24) SD Card

Solution

A- Exchange the J801 to see if the problem is solved, if yes, It is the problem of the TF socket;
B- Replace U300

U300

J800

J802

Model X771 L3 Service Manual

25) SIM Card

Solution

C- Exchange the J800 or J802 to see if the problem is solved, if yes, It is the problem of the sim socket;
D- Replace U300

Model X771 L3 Service Manual

Thanks

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