cromax C2A User manual

C2A L3 Service Manual
A) Technical Specifications:
Particular
Remarks
Key Matrix For Flashing
NO
Chipset
MT6737V/WHA
Android Version
7.0
Frequency
GSM 2/3/5/8, WCDMA 1/8, FDD1/ 3/ 5, TDD 40/41
Network Mode
SIM1: GSM+WCDMA+LTE
SIM2: GSM
Rom
32GB
RAM
24Gb
Internal SD Card memory
YES
Expandable Memory
NO

C2A L3 Service Manual
Factory mode code
*#*#21719*#*#
Good Earpiece volume
YES
Good Loudspeaker volume
YES
Good MIC volume
YES
Good Vibrator volume
YES
Engineering Code
B) 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.

C2A L3 Service Manual
C) L3 Service Manual
J901 earphone
connect
J1002 Front cam
connect
U706 charge IC
J1801 T-card&SIM
connect
J1101 LCD
connect
Q1001 Front
Flash IC
U4102 Memory
U101 CPU
U2001
PMU IC

C2A L3 Service Manual
J1202 sidekey
connect
J702 Battery
connect
U1403 4G PA
U802 Rear
Flash IC
D805 Rear
Flash LED
J1001 Rear cam
connect
J502 SUB
Board connect
U801 backlight
IC
U1700 WCN IC
U1507 2G PA
U1300 RF
Transceiver
J501 Finger
connect

C2A L3 Service Manual
D) Symptoms
1. Unable to load Software:
2. RF ISSSUE:
2.1 LTE part

C2A L3 Service Manual
LTE/WCDMA Multi-mode PA :
PrimaryAntenna port:
Diversity Antenna port:

C2A L3 Service Manual
Antenna switch receiving ports:
For FDD-LTE(primary) band1 signal comes from primary antenna switch through duplexer U1506 and matching circuit to transceiver RX
ports.
For FDD-LTE(primary) band3 signal comes from primary antenna switch through duplexer U1509 and matching circuit to transceiver RX
ports.
For FDD-LTE band5(primary) signal comes from primary antenna switch through duplexer U1513 and matching circuit to transceiver RX
ports.
For TDD-LTE band40/41(primary) signal comes from primary antenna switch through saw U1520 and matching circuit to transceiver RX
ports.
For TDD/FDD LTE band1/3/5/40/41 (diversity ) signal comes from diversity antenna switch through saw U1607/U1606/U1605/U1603/U1609

C2A L3 Service Manual
and matching circuit to transceiver RX ports
2.2 WCDMA RF power trouble
Check points
-PA connector soldering
-Duplexer connector soldering
-Other Tx RF Component soldering
Wcdma Band I&VIII

C2A L3 Service Manual
For WCDMA RF power:
Step1:check PA connector soldering is ok, if no,,reslodering or repalace
Step2:check duplexer connector is ok, if no,,reslodering or repalace
Step3:check other Tx RF component soldering if no is ok ,reslodering or repalace
2.3 GSM RF power trouble
Check points
-Tranceiver connector soldering
-PA connector solderin

C2A L3 Service Manual
2.4 WCDMA RX trouble
Check points
-Tranceiver connector soldering
-Duplexer connector soldering
-ASM switch connector soldering
-Other Rx RF Component (L/C) soldering

C2A L3 Service Manual
Wcdma Band VIII -RX
Wcdma Band I - RX
For WCDMA Rx issue:
Step1:check Tranceiver connector soldering is ok, if no,,reslodering or repalace
Step2:check duplexer connector is ok, if no,reslodering or repalace
Step3:check ASM Switch soldering is ok, if no,reslodering or repalace
Step4:check other Rx RF component soldering if no is ok ,reslodering or repalace

C2A L3 Service Manual
2.5 GSM RX trouble
Check points
-Tranceiver connector soldering
-ASM switch connector soldering
-Rx SAW filter connector soldering
-Other Rx RF Component (L/C) soldering

C2A L3 Service Manual
For GSM Rx issue:
Step1:check Tranceiver connector soldering is ok, if no,,reslodering or repalace
Step2:check duplexer or rx SAW soldering is ok, if no,reslodering or repalace
Step3:check ASM Switch soldering is ok, if no,reslodering or repalace
Step4:check other Rx RF component soldering if no is ok ,reslodering or repalace

C2A L3 Service Manual
2.6 WiFi/BT/GPS Part
2.6.1 WIFI/BT/GPS Part
GPS LNA part

C2A L3 Service Manual
WIFI BT share RF access, signal is entered by antenna, through U1702 2.4GHZ filter, filter sideband unwanted signal.
The clock uses 26M clock provided separately. Data transfer interface and audio interface are directly connected to the CPU.
Interface has SDIO is used for the WIFI signal transmission; PCM is used for the BT signal transmission.
WIFI main problems：
1. MT6625L chip has been calibrated before out of factory, production line directly do FT test. The probability that it
appears problems by WiFi test is very low, the FT failure problems, please power off and restart the phone, first retest.
2. Wifi power test fail, please re-test, failed again to check whether the devices U1702 on the launch access has solder
skips, and channel RC device.
3. WIFI test EVM fail. This major and power, as well as the freq error, if the power is too high or the freq too big EVM
may also lead to excessive, please re-test.
4. WIFI RX fail, main receiving sensitivity fails to pass, check whether U1702 has solder skips. Generally, production line
testing has not shielded box, RX vulnerable to external signal interference, If come across such problems, can change
the channel to do the test.
Bluetooth main problem：
Bluetooth does not need calibration, only need to check the function, if unable to search the device or Bluetooth can not
be opened, check whether the U1700 is welding bad or body bad.

C2A L3 Service Manual
GPS main problem：
GPS signal first enters the GPS saw U1703 and U1704, after saw, input to MT6625L chip within, demodulate signal .
The GPS fails to search satellite or the search- satellite GPS_REG_ON value is high, focus on checking the U1703 and
U1704 filters paste partial or Weld, then check the tcxo power supply of VDDRF0, four voltage normal check whether the
UART single working. If the power supply and may UART no working ,please check the MCP MT6625L
Thanks
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