Micromax Q392 Service manual

Q392 L3 Service Manual

1. Technical Specifications :

Particular

Key Matrix For Flashing

Chipset

Android Version

Processor Frequency

Network Mode

ROM

RAM

Internal memory

Expandable Memory

Factory mode code

Good Earpiece volume

Good Loudspeaker volume

Good Mic volume

Good Vibrator volume

Remarks

N/A

MTK6580 Quad-core

Android L

1.3GHz

3G WIFI

8GB

2GB

5GB

32GB

*#87#

32 ohm

4 ohm

2200 ohm

32 ohm

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.

Q392 L3 Service Manual

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. Q392 Level trouble shooting

1) Doesn’t Power On

Solution:

 There is no current when the Power Key is pressed; check J1307 to see if there is false soldering, pseudo soldering or damage, if yes, Carry out Resoldering or replacement;

 There is no display when the Power Key is pressed, and the current stays within 100~120mA, if yes, The problem is caused by pseudo soldering or damage of the MCP (U101);carry out repair soldering or replacement of the

MCP;

 When the Power Key is pressed, the display freezes in a certain interface, if yes, Upgrade the software version;

It should be caused by pseudo soldering or damage of PMIC(U401);

 There is heavy current when the Power Key is pressed, if yes, Find the hot point, and replace the corresponding material (PMIC (U401) and CPU (U101) are damaged in most cases.

Battery Connector

Q392 L3 Service Manual

2) Restart / Hang

 When the Power Key is pressed, the display freezes in a certain interface, if yes, Upgrade the software version;

 There is no display when the Power Key is pressed, and the current stays within 100~120mA, if yes, The problem is caused by pseudo soldering or damage of the MCP ( U501 );carry out repair soldering or replacement of the

MCP;

 There is heavy current when the Power Key is pressed, if yes, Find the hot point, and replace the corresponding material (PMIC ( U401 ) and CPU ( U101 ) are damaged in most cases).

3) LCD Issues “Black screen and no display of LCD”

Solution:

 Exchange the front shell to judge if the LCD itself is abnormal, if yes, Replace the LCD;

 Check if the LCD connector is damaged (such as burnout) , if yes, Replace the LCD connector XJ801;

 Check if the diode D802 in the backlight circuit is soldered abnormally or damaged, if yes, Carry out repair soldering or replacement of D802;

 Check if the power inductor L801 in the backlight circuit is soldered abnormally or damaged, if yes, Carry out repair soldering or replacement of L801;

 Replace the backlight driver IC (U801).

Q392 L3 Service Manual

Display problems such as black screen, white screen and blurred screen when the backlight is OK.

Solution:

 Exchange the front shell to judge if the LCD itself is abnormal, if yes, Replace the LCD;

 Check if the LCD connector is damaged, if yes, Replace the LCD connector XJ801;

 Check if the EMI components (EMI801, EMI802, EMI803,EMI804) connected in series on the LCD MIPI signal line are soldered abnormally or damaged, if yes, Carry out repair soldering or replacement;

 Replace U101.

Q392 L3 Service Manual

4) Touchpad Failure

Solution:

 Exchange the front shell to judge if the TW itself is abnormal, if yes, Replace the front shell (with LCD);

 Check if the LCD/TP connector is damaged, if yes, Replace the main LCD/TP connector XJ801;

 Replace

U101

 Replace Touchpad

5) Proximity Sensor “Test failure of the light/proximity sensor”

Solution:

 Check if the silicon case for light/proximity sensor is properly installed, if yes, Reinstall the silicon case for light sensor ;

 Check if the sensor have damage or pseudo soldering, if yes, Replace the sensor;

 Check if the I2C pull-up resistors of the acceleration sensor are OK, if yes, Carry out repair soldering of resistors R306 and R307 ;

 Replace

U101 .

Q392 L3 Service Manual

6) Accelerometer “Failure to realize automatic screen rotation during image viewing”

Solution:

 Check if the voltages of C900（1.8V）and C901（2.8V）, respectively, if yes, Carry out repair soldering or replacement;

 Check if the IIC pull-up resistors R306 and R307 of the acceleration sensor have pseudo soldering, if yes,

Carry out repair soldering or replacement;

 Replace U908.

Q392 L3 Service Manual

7) Keypad

 There is no current when the Power Key is pressed, or volume keys do not work, please exchange the key

FPC;

 Check if R401,R1324 andR1325 is soldered abnormally or damaged, if yes, Carry out repair soldering or replacement of them;

 Check if ESD component FV1320, FV1321 and FV1331 are soldered abnormally or damaged, if yes, Carry out repair soldering or replacement of them;

 Replace U101

8) Charging Failures “

No indication during charging”

Solution:

 Check if the charging IC

D402 is abnormal, if yes, Carry out repair soldering or replacement;

 Check if the pull-up resistors

R304 and R305 of the charging IC are abnormal, if yes, Carry out repair soldering or replacement;

 Check if the problem is solved after replacement of the PMU

U401 , if yes, It is problem of the PMU U401 ;

 Replace the

U101 .

Q392 L3 Service Manual

There is charging indication, but no charging current.

Solution:

 Check if there is any obvious damage on the surface of the charging IC U902, if yes, The charging IC is damaged; replace U902;

 Replace L407 and R328.

9) USB “Failure of Connecting the Phone to the PC via the USB Data Cable

”

Solution:

 Check if the connector XJ103 is damaged or has pseudo soldering, if yes, Carry out repair soldering or replacement of the material;

 Check if D401, FV109,FV110 are abnormally soldered or damaged, if yes, Carry out repair soldering or replacement of the TVS tubes;

 Replace U101.

10) Main Camera “Photographing and Shooting Failures”

Solution:

 Check if the camera is properly installed, if yes, Reinstall it;

 Exchange the camera to see if the problem is solved, if yes, The problem is caused by the camera itself; replace it;

 Check if the camera connector has pseudo soldering or damage, if yes, Carry out repair soldering or replacement of XJ701

 Check if the IIC pull-up resistors R302 and R303 have pseudo soldering, if yes, Carry out repair soldering or replacement of R302 and R303.

11) Front Camera “Photographing and Shooting Failures”

Solution:

 Check if the camera is properly installed, if yes, Reinstall it;

 Exchange the camera to see if the problem is solved, if yes, The problem is caused by the camera itself; replace it;

 Check if the camera connector has pseudo soldering or damage, if yes, Carry out repair soldering or replacement of XJ702;

 Check if the IIC pull-up resistors R302 and R303 have pseudo soldering, if yes, Carry out repair soldering or replacement of R302 and R303.

Q392 L3 Service Manual

12) Flash Light “Malfunction of Torch or Flashlight”

Solution:

 Check if the camera can be turned on, if yes, The problem is caused by the rear-facing camera; see the analysis of camera failures;

 Check if the light can turn on when battery voltage is supplied to its both ends, if yes, Replace the light

HL902;

 Replace U700.

13) Vibrator Failures

Solution:

 Check if the vibrator has pseudo soldering or damage, if yes, Carry out repair soldering or replacement;

 Replace U401.

Q392 L3 Service Manual

14) Sim “Failure to identify SIM card”

Solution:

 Check if the SIM card sockets J1301andJ1303 is obviously damaged, if yes, Replace the SIM card socket;

 Check if the pins of the SIM card sockets J1301andJ1303 have pseudo soldering, if yes, Carry out repair soldering;

 Check if the ground impedance of each pin of the SIM card sockets (except the ground pin) is low (lower than grade K) , if yes, Replace U401;

 Replace U401

15) Network /GPS / WI-FI “Weak signals of main antenna and GPS and WIFI antennas”

Solution:

 Check the surfaces of the main antenna and the GPS and WIFI antennas to see if there is any crease or breakage;

 Check the gold fingers of the main antenna and the GPS and WIFI antennas to see if there is any breakage and if the gold fingers are in good contact;

 First, it is needed to check the matching parts of the main antenna and the GPS and WIFI antennas to see if there is pseudo soldering or missing part, and check if the cables and the corresponding sockets are in good contact.

Q392 L3 Service Manual

Abnormality of coupling power.

Solution:

Abnormality of coupling power often occurs in calibration and integrated test of the production line.

Generally, this problem can be solved according to the following steps:

First, test the conduction power to see if it’s normal; if normal, then test the circuit between the RF test socket and the antenna to see if it is normal; or else, see the analysis of “Abnormality of

conduction power”.

The steps for testing the circuit between the RF test socket and the antenna to see if it is normal are shown in the following chart:



T est the conduction power to see if it normal, See “problem of low conduction power” for details.

Check if the contact between the antenna and the antenna spring clip is normal. Replace the antenna connector according to the antenna requirements.

Check if the circuit between J1002 on sub-board and the antenna spring clip is normal. Check the RLC elements on the circuit to see if there are problems like pseudo soldering and open circuit.



Check if the cable between J1002 on main board and J1002 on sub-board is normal. Replace the cable.



Check if J1002 on main board and J1002 on sub-board are normal. Replace them with new RF connection sockets.

C heck if the circuit between J1002 on main board and J1001 on main board is normal.

Abnormality of this section of circuit is mostly caused by the problem of PCB, which cannot be repaired basically; therefore, the only solution is to replace the main board.



End.

2G/3G related circuit picture

Main board J1001 and J1002 on the schematic and related components on the pcb

Q392 L3 Service Manual

Sub board J102 on the schematic and related components on the PCB

Abnormality of conduction power

Solution:

There are many causes of abnormality of conduction power. The basic causes include:

① Damage of component material in the RF circuit, which can be solved by replacing the material;

② Pseudo soldering of components, which can be solved by repair soldering;

③Direction error or position shift of components due to surface mounting, which can be solved by properly soldering the components;

④ Power abnormality caused by abnormal calibration 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 details as below:

2G GSM TXM circuit on the schematic and related components on the PCB

2G GSM receive circuit on the schematic and related components on the pcb

Q392 L3 Service Manual

3G WCDMA B1&B8 TX&RX circuit on the schematic and related components on the PCB

PS: To be sure, the WCDMA BAND8 TX and RX link are cross the BAND5 path in the schematic, which is just considering the compatibility design, not the wrong design.

16) WIFI Failures

Solution:

WIFI cannot be turned on, if yes, Replace U101 WIFI/BT/GPS/FM 4 in MT6580.



WIFI cannot be connected, if yes: Check if J1201 are soldered incompletely or have dry soldering.

The components

WIFI/BT/GPS/FM related circuit picture

WIFI/BT/GPS/FM 4 in MT6580 related circuit on the schematic and related components on the pcb

Q392 L3 Service Manual

BT/WIFI Circuit on the schematic and related components on the pcb

17) BT Failures---Please refer same with WIFI

BT use the same circuit with WIFI, related failures please refer same with WIFI

18) GPS Failures---Please refer with WIFI

Positioning failure of GPS, if yes:

Check i f U1202 and U1201 are soldered incompletely or has pseudo soldering. Carry out repair soldering of the components.

GPS circuit on the schematic and related components on the PCB

Q392 L3 Service Manual

19) FM Failures - Please refer with WIFI

Positioning failure of FM, if yes:

Check if the

U101

is soldered incompletely or has pseudo soldering. Carry out repair soldering of the components or replace it by a new one.

20) Heating Issues - Please refer same with Power-On failure.

21) Ear Phone “There is no sound from the earphone when an audio file is played”

Solution:

 Visually inspect the earphone jack to see if there is any abnormality, if yes, Replace the earphone jack J603;

 Check if Z601, Z602, Z603 and Z604 have pseudo soldering, if yes, Carry out repair soldering;

 Replace U401.

There is no voice received from the earphone via WCDMA/GSM network.

Solution:

 Visually inspect the earphone jack to see if there is any abnormality, if yes, Replace the earphone jack J603;

 Check if Z601, Z602, Z603 and Z604 have pseudo soldering, if yes, Carry out repair soldering;

 Replace U401.

Abnormality of the earphone found through inspection.

Solution:

Q392 L3 Service Manual

 Visually inspect the earphone jack to see if there is any abnormality, if yes, Replace the earphone jack J603;

 Check if Z601, Z602, Z603 and Z604 have pseudo soldering, if yes, Carry out repair soldering;

 Replace U401.

Earphone MIC Circuit

22) Outgoing Audio / MIC “There is no voice transmitted by the local MIC via WCDMA/GSM

network”

Solution:

 Exchange the main FPC to judge if the FPC itself is abnormal, if yes, Replace the main FPC;

 Exchange the sub board to judge if the sub board itself is abnormal. , if yes:

① Problem of the main FPC connector J1305 on the mainboard;

② Problem of U401.

 Check if the MIC is offset, and if the MIC to ground impedance is abnormal, if yes, Replace the TVS tube FV103 or FV104;

 Check if the M601 itself is abnormal, if yes, Replace the M601.

Q392 L3 Service Manual

There is no voice transmitted by the earphone MIC via WCDMA/GSM network.

Solution:

 Visually inspect the earphone jack to see if it is abnormal, if yes, Replace the earphone jack

J603;

 Check if Z603,FV601,C610,C608,C609and C612 have pseudo soldering, if yes, Carry out repair soldering;

 Replace U401.

Q392 L3 Service Manual

23) Incoming Audio / Earpiece “There is no voice received from the receiver via WCDMA/GSM

network”

Solution:

 Exchange the front shell to judge if the receiver itself is abnormal, if yes, Replace the receiver;

 Check if the receiver pad to ground impedance is lower than grade K, if yes, Replace C626,

C627, C628, FV605 and FV606 on the mainboard;

 Check if R612 and R613 have pseudo soldering, if yes, Carry out repair soldering;

 Replace U401.

Q392 L3 Service Manual

24) Speaker “There is no sound from the speaker when an audio file is played”

Solution:

 Exchange the back shell to judge if the speaker itself is abnormal, if yes, Replace the speaker;

 Check if L604 and L605 have pseudo soldering or damage, if yes, Carry out repair soldering;

 Replace the audio PA U604;

 Replace U401.

There is no voice received from the speaker via WCDMA/GSM network.

Solution:

 Exchange the back shell to judge if the speaker itself is abnormal, if yes, Replace the speaker;

 Check if L604 and L605 have pseudo soldering or damage, if yes, Carry out repair soldering;

 Replace the audio PA U604;

 Replace U401.

Q392 L3 Service Manual

25) Memory Card “Failure to identify TF card”

Solution:

 Check if the TF card socket J1304 is obviously damaged, if yes, Replace the TF card socket;

 Check if the ground impedance of each pin of the TF card socket (except the ground pin) is low (lower than grade K) , if yes, Replace the varistor of the corresponding pin;

 Upgrade the software.

 Replace U101

Thanks

For any Query or suggestion, Please write to [email protected]