Asus ZD553KL User manual

ASUS ZD553KL Service Manual
2017-06-08 ZD553KL -1-
ZD553KL
（L3-L4)
Customer Service Manual
Version : v1.0

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一：Overview
1.Specifications………………………………………………………………………………………………………………………...……………..3
2. The main function …………………………………………………………………………………………………….…………………………3
二：Mobile phone structure diagram
1. ZD553KL Motherboard PCBA diagram
……………………………………………………………….…………………………………4
2. Main chip work principle…………..……………………..…………………………………………………………………………………..7
三： Common Fault Analysis
1.Boot class fault……….………………………………………………………………………………………………………………..…………12
2.Display class fault…………………………….……………………………………………………………………………………….…………16
3.Sound class fault………………………………………………………………….……………………………………………………………...19
4. Touch screen fault………………………..…………………………………………………………………………………………………….29
5. Charging fault…………………………..…………………………………………………………………………………………………………28
6. Motor fault……………………….…………………………………………………………………………….……………………….…………33
7. SIM/UIM/T Card identification fault…………………….…………………………………………………………………………….35
8. Camera type
failure………………………………….…………………………………………………………….…………………………..39
9.GPS/WIFI/BT failure……………………………………………………….……………………………………………………………………44
10.FM demodulation circuit
failure…………………………………….……………………………………………………………………47
11. Front and rear flash bad…………………………….………………………………………………………...……………………………50
12. Light distance sensor failure………………………………………………………………………………………..…………………….52
13.Gyrosensorfault …….……………………………………….………………………………………………………………………………….54
RF class failure（ Refer to RF bad analysis）
Contents

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一、Overview
1、Specifications：
1)Network frequency : GSM：900/1800/1900MHz , GSM：B2(1900)/B3(1800)/B8(900)；
TDD LTE： B38(2600)/B39(1900)/B40(2400)； TD-SCDMA： B34(2010)/B39(1900)；
2) size: 154.8mm×77.8mm×8.8mm
3) screen: 5.5 TFT /1280*720 /HD/IPS
4) Battery: 3000mAh lithium battery
2、The Main Function:
1) Front Camera: Front dual Camera: F2.0 20M FF OV20880-4C + 8M F2.2 Wide angle 120 ° optical
Compatible with previous single Camera: 13.0M FF;
Main Camera: F2.2 16M AF OV & SAMSUNG; Compatible with 13.0M AF;
2) Flash LED: Front and rear single flash
3) SIM: Dual SIM Dual Standby (Nano-SIM slot*2) support DSDS 4G+3G (Sim1, Sim2 support LTE
interchangeable),SIM Tray Keep Nano SIM*2+micro SD 3 election 3
4) Sensor:
1. Accelerator
2. E-Compass
3. Proximity
4. Ambient light sensor
5. Gyroscope6. Hall sensor
5) Fingerprint recognition: Support, front
6) Microphone: Microphone*2 (one for de-noise)
7) Storage: eMMC 32G, Micro SD Card Support (Up to 2TB) (SD Card slot * 1), 2G/16G,3G/32G
8) Charger: Charging LED must be included, JEITA, USB-ACA standard supported

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二：Mobile phone structure diagram
1. ZD553KL Motherboard PCBA diagram

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2.Main chip work principle
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PM8937 Work Principle

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PM8937 Power on sequence

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Power on timing specifications

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三： Common Fault Analysis
1. Boot class fault

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1)power supply IC to work properly, must have a working voltage, the voltage is generally the battery
voltage or external power supply voltage.
2) boot trigger signal added to the power supply IC, press the power button, the trigger signal to start
the level of change.
3) Power supply IC is generally integrated with multiple groups of controlled and uncontrolled voltage
regulator circuit, when there is a trigger signal, the power supply IC regulator output should be voltage
output.
4) Have the power on hold signal (watchdog signal). Power-on maintenance signal from the CPU, power
IC only to get the power to maintain the signal to continue after the output voltage.
Use the external power supply, it is best to have the output current and output
voltage display, and there is current protection, encounter short circuit case, will
automatically cut off the output current, the phone will not have greater damage,
adjust the power supply voltage of 4.0 V, the output can supply current of 2.0A is
appropriate. To PCBA power on the boot, pay attention to the battery near the
connector pin to connect the 10K to the ground resistance to simulate the battery in
place. Otherwise it can not boot
Use the external power supply, it is best to have the output current and output
voltage display, and there is current protection, encounter short circuit case, will
automatically cut off the output current, so that the phone will not have greater
damage, adjust the power supply voltage of 4.0 V, the output can supply current of
2.0A is appropriate. Through the fake battery to the PCBA power test.
1）Power on the first press the power button to observe the shutdown leakage
current, if the leakage current is very large, focus on checking with VBAT connected
devices, with a multimeter to check the power supply (VBAT) to ground and VBUS to
ground whether there is a short circuit, Short circuit phenomenon, please first
check whether the relevant ESD protection device is punctured, and then on the VBAT
network related to some of the devices are damaged or short circuit phenomenon, the
principle is the first easy, first to exclude some easy to judge the part.
2. current boot is too small after about 10MA, the common main clock does not work, check the 19.2M
X0501 clock oscillator, U1500 chip, power management chip U0501 and U0401, and peripheral devices
have no weld, even tin, power supply is normal.
3）Press the power button after the basic current 100 ~ 200mA up and down, common
software is bad, you can re-download the program test. Such as troubleshooting
software problems can not be downloaded, it is likely that the main chip U1500 or
memory U1501 Welded loose or damaged
4）Press the power button after the current is very large, hundreds of milliampere
phenomenon, causing current protection, focusing on power supply timing diagram,
Check the power output to the ground whether there is a short circuit phenomenon, if
there is a short circuit, followed by the power of the device.

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check if
the 19.2M
crystal is
work
change the 19.2M crystal
or solder it again

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2. Display bad fault
analysis
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LCD display data from the CPU output after each EMI device, through the FPC
transmission to the screen. Therefore, for screen display failure, general analysis is
as follows:
1. Check if the LCD connector J1705 welding good dirt phenomenon, to see if there is
any breakage.
2. The working voltage is normal. If abnormal, check the welding condition of PMU
3. Check the LCD control signals' LCM_FMARK ', 'LCM_RSTN' pathways and circuit
device is normal, including LCD_ID is less effective.
4. Check the LCD MIPI signal lines' TCN&P, TDP0 & N0, TDP1 & N1 "EMI Filter device for
welding or performance issues.

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LCD backlight control signal U0401 boost, the output through the LCD connector J1705 input LCD.
Therefore, if the LCD backlight, the failure is generally analyzed as follows:
1. Check the LCD screen solder joints are good, especially the backlight control signal "LEDA", "LEDK" two
pins
2. Check LCD backlight "LEDA" (18 v) voltage is normal, the line device on the feedback signal "LEDK"
normal.
3.LCD backlight "LEDA" abnormal voltage, first check U0401 welding problems and peripherals, check the
enable signal "LCM_BL_PWM" is normal.
4. Start signal "LCM_BL_PWM" is not normal, check whether the output of the CPU is welded or replaced.

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3. Sound class fault
MIC fault analysis

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This machine is designed for dual microphone, which is located in the bottom of the motherboard
MIC1101 main microphone, through the FPC to the motherboard, to provide normal send function,
located at the top of the motherboard MIC1600 for the auxiliary microphone, to provide noise reduction
function, the normal work, The microphone provides a bias voltage, the microphone starts to pick up,
and the signal passes through a coupling capacitor into the power supply chip.