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L3 Service Manual
1. Technical Specifications :
Particular
Remarks
Key Matrix For Flashing
N/A
Chipset
MTK6580
Android Version
Android L
Processor Frequency
1.3GHz
Network Mode
3G WIFI
ROM
8GB
RAM
2GB
Internal memory
5GB
Expandable Memory
32GB
Factory mode code
*#87#
Good Earpiece volume
32 ohm
Good Loudspeaker volume
4 ohm
Good Mic volume
2200 ohm
Good Vibrator volume
32 ohm
Quad-core
2. CAUTIONS
I.
II.
III.
IV.
Flashing & Servicing must be undertaken by qualified personnel only.
Ensure all work is carried out at an anti-static workstation and that an anti-static wrist strap is
worn.
Use only approved Tools & components as specified in the parts list.
Ensure all components, modules, screws, and insulators are correctly re-fitted after servicing
and alignment.
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L3 Service Manual
Ensure all cables and wires are repositioned correctly if Handset disassembled
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
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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).
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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.
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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 .
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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.
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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.
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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.
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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.
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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.
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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:
Test 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.
Check 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
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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
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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
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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 if 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
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19) FM Failures - Please refer with WIFI
Positioning failure of FM, if yes:
Check if theU101 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:
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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.
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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.
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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.
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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.
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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
tech.help@micromaxinfo.com
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