FLY SERVICE SUPPORT
IQ4490i Service Manual V1.0
FLY SERVICE SUPPORT
Contents
1. IQ4490I overview ................................................................................................................. 3
1.1 IQ4490I brief introduction .................................................................................................. 3
1.2 Function diagram ................................................................................................................ 4
1.3 Mainboard component distribution diagram ....................................................................... 5
1.4 Main IC Names ................................................................................................................... 7
2. RF ......................................................................................................................................... 8
2.1 WCDMA RF power trouble ................................................................................................ 8
2.2 GSM RF power trouble .......................................... Ошибка! Закладка не определена.
2.3 WCDMA RX trouble ........................................................................................................ 11
2.4 GSM RX trouble ............................................................................................................... 12
2.5 WiFi/BT Part .................................................................................................................... 14
3. Baseband section ................................................................................................................ 15
3.1 Outline .............................................................................................................................. 15
3.2 Common Failure Analysis and Maintenance .................................................................... 17
3.2.1 Power failure Check .............................................................................................. 17
3.2.2 Audio faults ........................................................................................................... 18
3.2.4 LCD Fault .............................................................................................................. 21
3.2.5 FM ......................................................................................................................... 22
3.2.6 Camera fault ................................................................................................................... 22
3.2.7 SIM card failure .................................................................................................... 23
3.2.8 Motor test is invalid ............................................................................................... 24
3.2.9 Gravity Sensor ....................................................................................................... 24
3.2.10 T-Flash fault ......................................................................................................... 25
3.2.11Touch Panel function ............................................................................................ 26
3.2.13 Cannot boot failure .............................................................................................. 26
FLY SERVICE SUPPORT
1. IQ4490I overview
1.1 IQ4490I brief introduction
The development and design of the IQ4490I PCBA is based on SC7715A platform. The mainboard system mainly
consists of the chip SC7715A+SR2351 +SR3131, which are responsible for three part functions, namely, baseband,
radio frequency and power management chip. IQ4490I PCBA is an all-in-one phone mainboard, which supports GSM,
WCDMA, and covers Bluetooth, WIFI, Camera, FM functions, and so forth.
The maintenance of mainboard is one of the important links among mobile products rear-end producing. The
speed and quality of maintenance relate to the rate of good products, production efficiency, and cost control
throughout the producing. In the case of a reasonable design of product, in the end-producing, finding the significant
proportion in the bad board should be SMT bad and component incoming material bad. So, when maintaining, first,
start with the two aspects. The principal means of fault diagnosis are: (1) find that bad welding spots or components
by microscopic examination and visual inspection; (2) guess failure positions from the fault phenomena; (3) confirm
the fault units by signal detection.
1.2 Function diagram
FLY SERVICE SUPPORT
1.3 Mainboard component distribution diagram
Mainboard TOP
FLY SERVICE SUPPORT
Mainboard BOTTOM
1.4 Main IC Names
Ite
m
Description
PN
REF
1
SC7715A;570;FCVFBGA;13.3X12.1;040;BB;WCDMA
SC7715A
U201
2
IC,MEM,FBGA162,4GB/4Gb,6/1.9nS,e-
MMC/LPDDR2,4Gbx8/128Mx32,1.8V/3.3V,MCP,1.8/1
.2V,MCP
KMN5X000ZM-B209
U401
3
Chip Scale Packaged Fully Integrated Thermal
Accelerometer-2D-8bit-3*3mm-IO1.8V
MXC6255XC
U501
4
Electric Double Layer Capacitor-3.3V-0.033F-
13.8uAH-纽扣型-Φ3.8mm-高1.5mm
SM3R3333T01
U502
5
SR2351;38;QFN;5.5x4.5;040;RF
SR2351
U801
6
LDO; 3.3V; 300mA; 300mV; SOT23-5L
WL2801E33-5/TR
U802
7
Switch+PA;3.3V;2.4-2.5GHz,Small 16L QFN
2.5x2.5x0.45m㎥
RTC7626
U803
8
SAW;2450MHz;2.1;2.0;2x1.25x0.9
LFB212G45CL1D172
U808
9
SR3131;50;QFN; 5.5x7; 040; RF; 3G
transceiver
SR3131
U901
10
PA QuadBand GSM/GPRS and Dual-Band WCDMA
Handsets
• LGA 6mm x6mm x0.9mm
SC2662H
U902
11
PA Module for
WCDMA/HSDPA/HSUPA/HSPA+Application
• 3mm*3mm*0.9mm
SC2671H
U903
12
SAW DUPLEXER FOR UMTS BC1
SAYRF1G95HQ0F0A
U904
13
PA Module for
WCDMA/HSDPA/HSUPA/HSPA+Application
• 3mm*3mm*0.9mm
SC2678H
U905
14
SAW DUPLEXER FOR UMTS BC8
SAYFH897MHC0F0A
U906
15
晶体-32.768KHz-12.5PF-+/-20PPM-65kΩ-
7.0mm*1.5mm*1.4mm
Q13MC1462000200
X501
16
26M 8pF 10ppm Crystal NX3225SA
7V26000015
X901
FLY SERVICE SUPPORT
17
SAW FILTER FOR GSM1800/GSM1900 (Rx)
SAWEN1G84CV0F00
Z907
18
Gate;single;buffer with 3-state
output;0.8V~3.6V;sc70
SN74AUC1G125DCKR
U804
19
SAW滤波器-1575.42/1602MHZ-0.9DB-1.4*1.1*0.6
SAFEA1G58KA0F00
U805
U806
20
SiGe:C Low Noise Amplifier MMIC for GPS,
GLONASS and Galileo
BGU7005
U807
2.1 WCDMA RF power trouble
Check points
-PA connector soldering
FLY SERVICE SUPPORT
-Duplexer connector soldering
-Other Tx RF Component soldering
FLY SERVICE SUPPORT
Start
Replace PA
Check PA
connector
soldering is ok?
Yes
Check Dupolexer
connector is ok?
No
Resoldering
No
Resoldering
Yes
Check Other Tx RF
components
soldering is ok?
No
Resoldering
2.2 GSM RF power trouble
Check points
-Tranceiver connector soldering
-PA connector soldering
FLY SERVICE SUPPORT
FLY SERVICE SUPPORT
2.3 WCDMA RX trouble
Check points
-Tranceiver connector soldering
-Duplexer connector soldering
-ASM switch connector soldering
-Other Rx RF Component (L/C) soldering
FLY SERVICE SUPPORT
Start
Check Traceiver
connector
soldering is ok?
Yes
Check Duplexer
connector is ok?
No
Resoldering
No
Resoldering
Yes
Check Other ASM
Switch soldering is
ok?
No
Resoldering
Check Other
components(L/C)
soldering
2.4 GSM RX trouble
Check points
-Tranceiver connector soldering
-ASM switch connector soldering
-Rx SAW filter connector soldering
-Other Rx RF Component (L/C) soldering
FLY SERVICE SUPPORT
FLY SERVICE SUPPORT
Start
Check Traceiver
connector
soldering is ok?
Yes
Check ASM Switch
is ok?
No
Resoldering
No
Resoldering
Yes
Check Rx SAW
filter soldering is
ok?
No
Resoldering
Check Other
components(L/C)
soldering
2.5 WiFi/BT/ Part
2.5.1 WIFI/BT Part
FLY SERVICE SUPPORT
WIFI BT share RF access, signal is entered by antenna, through Z901 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.
FLY SERVICE SUPPORT
WIFI main problems：
1. SR2351 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 U808 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 U803 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 U801 is welding bad or body bad.
3.1 Outline
Baseband circuit completes main functions: the procedure data storage, keyboard input, and
the communication between the RF module, RF power control, the control of the power management
module, RUIM card interface, serial download interface, Camera, T-flash, Bluetooth, and MMI
(man-machine interface, such as the display, backlight, buzzer, speaker, microphone, motors,
etc.).
3.1.1 Memory
The baseband part has an eMMC/LPDDR2 MCP. Wherein the amount of eMMC storage 4GB, it stores
a communication protocol layer and application layer software, and storing various system
parameters, calibration parameters, such as RF control correction value of an audio signal, the
IMEI number, and other important information and store user settings data such as phone number,
CALL volume, and tone; LPDDR2 memory 1GB, temporary variables stored phone program run。
3.1.2 Power Management
3.1.3 Battery
FLY SERVICE SUPPORT
1500mAh 3.7V lithium-ion battery.
3.1.4 32KHzCrystal
32KHz crystal is used for power-saving mode and real-time clock。
If Xtal defective phone just entering the power saving mode will be closed。
3.1.5 SIM Card
SIM card interface is SIM card interface provided by SC7715A.
3.1.6 Audio frequency
The microphone is omnidirectional capacitor type. The largest impedance is 2.2K。
Headset as a standard 3.5mm headphone jack port, the nominal resistance 32。
Speaker adopts 11*15 specification, Receiver adopts 12*06 specification.
3.1.7 I/O Interface
I/O Connector MICRO USB interface standard. Mainly used for software, download picture
messages。
3.1.8 Display
The main screen is 3.9 inch。3.9-inch color screen 480*800（WVGA）.
FLY SERVICE SUPPORT
VDDCORE
1.1V
VDDARM
1.2V
VDDMEM
1.2V
VDD2V5
2.5V
VDD2V8
2.8V
VDDCON
2.85 V
3.2 Common Failure Analysis and Maintenance
Before cutting board after the completion of the production line SMT X-RAY inspection, according to the actual
situation, X-RAY examination can not be found 100% badness, X-RAY inspection may omissions some fault plate flow
down. If found fault plate in the testing process, the first step is to re-check of the X-RAY and carefully to see if there
is even welding, lap welding, Weld, if normal, analyze the situation following the positioning。
3.2.1 Power failure Check
The failure phenomenon caused by a power failure: can not boot, shutdown leakage current boot large current.
The main reason for the problem: Weld, electrical the original filtering or ESD device to short-circuit, burning with the
device is connected to a power source.
Positioning as well as steps to solve this type of problem is as follows：
1， Troubleshoot and connected to the power supply components of the welding, Weld, or the peripheral devices
even tin。
2， with a multimeter rule out whether there is power to short-circuit, and step by step to troubleshoot the cause
of the short (mainly: even tin, IC burned ESD protection device breakdown, capacitor breakdown)。
3， boot to test the power output is normal。
If a power output value is not normal, whether the view filter capacitor welding problems, whether the
breakdown, filter capacitor is broken, replace; excluded one by one, and finally you can navigate to the main chip
damage。
Each the power test position and the normal boot value is shown in the following table
FLY SERVICE SUPPORT
3.2.2 Audio faults
The audio part has main four parts including the speaker, receiver, mic and headphone.
First undesirable phenomena distinguish what part of the problem, and then analyzed according
to the following respective module.
（1）Speaker loop
The IQ4490I phone’s speaker circuit is as follow
Speaker Loop
Speaker Common faults and reasons：
1， SPK Ringtones reasons: 1) light board, SPK itself is bad, or the connection FPC problem, the whole
observation board board PFC Cartridge is skew, not in place 2) relevant component there is dry
welding 3 ) software problems
2: SPK ringtones or murmur: 1) software volume settings 2) SPK ontology reasons
3. Switch machine ringtones, but engineering tests SPK OK: 1) scene mode is set to switch machine ringer off 2)
software problems, itself boot ringtones;
(2) Receiver circuit
IQ4490I phone receiver is embedded in the mobile phone front shell through shrapnel and motherboard
connection. Mainly used for the call. Receiver circuit diagram as shown below.
FLY SERVICE SUPPORT
Receive Loop
Receiver Common faults and reasons：
1, Receiver without sound: 1) Receiver assembly adverse, the shrapnel and board poor
contact 2) Receive ontology bad 3) the volume settings or software problems
2, Receiver noise or volume: 1) Receiver incoming material, whether caused by pad short
circuit 2) relevant components have solder skips 3) software problems
(3) Mic loop
The AW660A contains two MIC circuits, the main MIC and headphone MIC. The main MIC was inserted
needle. Loop schematic diagram as following:
Main MIC common faults and causes
1 MIC unable to send words or recording: 1) MIC poor welding 2) MIC body bad
2 MIC noise or sound: 1) MIC ontology bad 2) software problems.
Main MIC
FLY SERVICE SUPPORT
（4）Headphone loop
IQ4490I phone use headphones with a standard 3.5mm headphone. Its circuit diagram is as follows:
Headphones common faults and reasons:
1, headphones only one channel sound: 1) the headset is not inserted in place 2) Relevant component Weld. 3)
Relevant component breakdown shorted to ground;
2 headphone left and right channels are no sound: 1) the headset is not inserted in place 2) Relevant
component breakdown on the short circuit;
3, unplug the headphones bank borrowing does not recognize: 1) Relevant component Weld; 2) whether
headphones Block shrapnel and motherboard good contact 3) software reasons
4 headset MIC no transmitter: 1) the headset is not inserted in place 2) Relevant component Weld 3) Relevant
component breakdown on short-circuit;
Headset MIC
3.5mmHeadphone jack circuit
FLY SERVICE SUPPORT
3.2.4 LCD Fault
3.5-inch HVGA LCD, The part of the circuit schematic as shown below. Common problems and causes of the LCD
module:
1, LCD screen is blank. 1) LCD is not installed or and fixture poor contact) LCD backlight circuit is bad, check
backlight so that the foot is pulled, check backlight IC whether Weld or shorted to ground. 3) LCD itself fault.
2, LCD blurred screen and white screen. Description LCD backlight circuit OK, just shows abnormal. The cause of the
malfunction is usually: 1) LCD connector poor contact, poor welding and fixture poor contact 2) related components
Weld or even tin short circuit 3) software problems
3. LCD black spots, bright spots, black lines, stripes Failure: LCD ontology bad.
FLY SERVICE SUPPORT
3.2.5 FM
The CPU controls FM IC working condition through the I2C signal, when FM is working, should insert headphone
as its antenna. FM outputs audio signal to the CPU Codec, amplify playing or record. FM common faults and causes:
1, FM cannot search frequency or less frequency reason: 1) headphone without inserting or not insert good 2)
surrounding environment is bad, such as plant, garage, etc. FM signals itself is weak or no FM signals source 3) FM
antenna circuit exists poor soldering or short circuit, lead to unable to receive FM signals or FM signals leak 4)
software reason
2，FM without sound reasons or murmur 1) this FM radio frequency is invalid 2) FM weak signal 3）related
component bad-welding 4) headphone was not put in place; 5) whether headphone socket shrapnel contacts with
the mainboard well 6) whether headphone socket welding is OK
3，FM module operation failed. 1）Check whether the I2C and CLK signal are normal or not 2）Software fault
3.2.6 Camera fault
Connect with the CPU through a dedicated Camera IF port. Camera control is done through the I2C bus. Camera
common fault and why:
1, Camera initialization failed, could not enter the Camera the main interface. 1) Camera poor welding or poor
contact 2) the Camera Ontology failure 3) Camera Power supply is not normal (Weld, or short-circuit led to) 4) related
components welding problems
2, Camera Preview shows blurred screen or color is not normal. 1) Camera poor welding or poor contact. 2)
related components welding 3) restore the factory settings after restart
3, Camera other problems, please replace the Camera try to confirm whether the Camera body has problems.
Back camera
3.2.7 SIM card failure
FLY SERVICE SUPPORT
Front camera
IQ4490I SIM card module circuit is connected directly with PMIC through eight-path signal from SUIM slot. The major
failure of the module does not know the card, the reason usually: 1) USIM card GSM card and USIM deck poor
contact 2) poor USIM card socket welding 3) software problem cause the phone to pick a card, change the card to
confirm. 4) SIM card holder exist Weld; 5) card exceeds the itinerary or inserted upside.
SIM card circuit
FLY SERVICE SUPPORT
3.2.8 Motor test is invalid
IQ4490I adopts flat motor, with simple circuit. As shown below. Common motor failures and the reasons are:
1, the motor without vibration 1) motor and motherboard contacted poor 2) motor body bad 3) whether the FPC
installed partial
2, the motor was felt as weak 1) motor ontology bad) the cause of the software settings
3 motor vibration sometimes 1) motor and motherboard poor contact
3.2.9 Gravity Sensor
IQ4490I G-Sensor circuit is very simple, Power offer power to the Sensor IC power, I2C bus transfer command
and data. G-Sensor faults and the reasons:
1, Sensor without functions: whether the paster is OK
FLY SERVICE SUPPORT
3.2.10 T-Flash fault
IQ4490I T - Flash circuit is connected with CPU through the special SDIO bus, circuit diagram shown below. T -
Flash the common faults and reasons are:
1, T–Flash read-write test is failure. 1) T - flash for fault card or and T kaka seat have had no contact with good 2)
below the resistance there may be short circuit, or virtual welding phenomenon. Capacitance may on short circuit.
(using a multimeter to test whether T card signal and ground and VMCH short circuit can eliminate) 3) software
reason
2, T card not to know card: T holder PIN feet virtual welding, on MLV welding reverse and capacitance
breakdown
3, T - Flash can't through the USB for transmission. 1) T - Flash itself, speaking, reading and writing test failure
fault 2) software fault 3) USB fault
T card circuit
FLY SERVICE SUPPORT
3.2.11Touch Panel function
Touch Panel common fault and reasons are:
1. The Sensor sensitivity low, slow reaction: software problem;
4. Touch Panel function NG, at present is mainly due to FPC itself partial long cause, the I2C initialization failed;
TP circuit
3.2.13 Cannot boot failure
Can't boot failure is the phone fault with highest probability of occurrence. Software problems, welding
problem, device failure is the main factor causing failing to boot. Maintenance process can cooperate with LCD and
startup current, as well as the keyboard and so on to orientate approximately.
1, Power off leak current is large. The main failure reason is VBAT connected components had to earth short
circuit problem. Usually radio frequency PA burned or welding problem cause. The simpler method is looking for is a
hot devices, general such devices have larger may on short circuit.
2, Boot without current, LCD no display, keyboard, etc not bright. 1) boot key SMT bad 2) battery connector bad
contact (through the plug charging machines)
3, Crashed when boot, 1）can try to re-download the software, 2）replace memory
4, Current is large when boot. LCD displays normally, even can enter the IDIE interface, single board is very hot
1) The individual power circuit short circuit to ground phenomenon exists in the phone, which is usually the problem
that ESD protective devices of module circuit breakdown short circuit to ground or weld problems.
Loading...