Asus ZENFONE T500 User manual

ASUS T500 MB Service Manual
Content
I. Baseband Troubleshooting Guide
1. System Block Diagram
2. Power Block Diagram
3. Power Domain and Power Sequence
II. MB Trouble Shooting Guide
I. Baseband Troubleshooting Guide ...............................................................................................................................1
II. MB Trouble Shooting Guide.......................................................................................................................................1
1. Outline and Component Introduction.........................................................................................................................4
2. Cannot power on...................................................................................................................................................5
3. Blank screen..........................................................................................................................................................6
4. LCD display failure ................................................................................................................................................7
5. TP does not work...................................................................................................................................................8
6. Light / Distance sensor failure...............................................................................................................................9
7. Gravity sensor failure...........................................................................................................................................10
8. Side key FPC failure............................................................................................................................................11
9. Cannot get charged, fail to identify USB.............................................................................................................12
10. Rear camera function failure.............................................................................................................................13
11. Front camera function failure.............................................................................................................................14
12.Flash failure........................................................................................................................................................15
13. GSM network failure..........................................................................................................................................16
14. CDMA network failure........................................................................................................................................18
15. LTE network failure............................................................................................................................................20
16. WIFI/ BT failure..................................................................................................................................................22
17. GPS failure ........................................................................................................................................................23
18. FM failure...........................................................................................................................................................25
19. Fail to identify earphone/Handset MIC failure...................................................................................................26
20. MIC no sound/small sound................................................................................................................................27
21. Receiver no sound.............................................................................................................................................28
22. Speaker no sound .............................................................................................................................................29
23. Fail to identify SIM card.....................................................................................................................................29
24. Fail to identify T-flash card ................................................................................................................................31

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I. Baseband Trouble Shooting Guide
1. System Block Diagram
2. Power Block Diagram

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3. Power Domain and Power Sequence

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II. MB Trouble Shooting Guide
1. Outline and Component Introduction
WIFI/GPS/FM IC
Flash
Earphone socket
26M Crystal
oscillator
Front camera connector
CPU MSM8916
KB connector
Battery connector
PMIC
Gravity
sensing IC
RF power
amplifier
LCD connector
Light/distance
sensor connector
WIFI/BT/GPS antenna
SIM socket
T-Flash socket
Flash
MIC
RF diversity antenna
PA&Main antenna
switch
26M Crystal oscillator
Flash driver IC
WIFI/BT/GPS module
RF switch
Audio PA
Backlight driver IC
RF switch
RF power
amplifier
SIM socket

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2. Cannot power on
Solution:
1Check if the battery connector and its soldering are oxidized or damaged
2Check if the following voltage, and GND has short circuit or abnormal voltage
VBAT 3.8--4.2V
VCORE 0.7--1.4V
VSYS 1.825/2.2V
VPA 0.5-3.4V
VTXCO 2.8V
VA 2.8V
VCAMA 2.8V
VCN28 2.8V
VCAMA 2.8V
VUSB 3.3V
VEMC_3V3 3.3V
3Check if start-up circuit is abnormal
4If the start-up circuit is about 20 MA, check if the soldering of crystal oscillator circuit is normal
5For those start-up current abnormally above 1A, check if VBAT circuit is shorted to ground, investigate each
locations’grounding diodes and other key components
6For those start-up current abnormally around 100MA, touch if there is any heating part on MB and focus on
their investigation
7X-ray: check each main chip’s soldering, CPU/Flash/PMIC(MSM8916/PM8916)
8Add soldering or re-solder each main chip and confirm again
9Replace CPU/Flash/PMIC
CPU MSM8912
Flash
PMIC
PM8916
Battery connector

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3. Blank screen
Solution:
1Check if the backlight chip U1704, driver chip U1780 has soldering deviation
2Check the LCD connector’s assembly is normal, if not please re-assemble
3Check if L1701(L1780)’s conduction is normal, and compare its’voltage on normal MB
4Check if D1702’s conduction is normal or the component’s soldering is reverse
5Check if LCD_BACKLIGHT_PWM’s signal is normal, and adjust this signal’s backlight brightness
6Check if VBAT’s power supply is normal

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4. LCD display failure
Solution:
1Re-assembly LCD or replace LCD, then reboot again to observe
2Check if LCD and its soldering is abnormal
3Check if LCD filter (FL1702,FL1704,FL1706,FL1708,FL1710) is poorly soldered or damaged
4X-ray: check if CPU’s soldering is abnormal
5Add soldering or re-solder CPU, or replace it
Backlight driver chip
L1780
LCD connector
CPU MSM8912
PMIC
PM8916
Backlight driver chip

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5. TP does not work
Solution:
1Re-assemble or replace the CTP, then reboot to test again
2Check if the CTP connector or its soldering is abnormal, re-solder or replace it to test again
3Measure if VREG_L6_1P8,R1506/VREG_L17_2P85,VD1509’voltage are normal
4X-ray: check CPU’s soldering, add soldering or re-solder it to test again
5Use a multi-meter to measure CTP test signal point, compare its ground resistance with normal MB’s
6Replace CPU
CTP connector
VREG_L17_2P
85

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6. Light / Distance sensor failure
Solution:
1Measure VREG_L6_1P8 R1504’s voltage
2Measure VREG_L17_2P85 R1501’s voltage
3Use a Oscilloscope to measure R1521’s VPH_PWR voltage, and check if the control signal is normal.
4Check if the connector is abnormal, re-solder or replace it to test again
5Add soldering or re-solder CPU, or replace it
Light / distance sensor connector
R150
4
CPU
R1501

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7. Gravity sensor failure
Solution:
1Measure VREG_L17_2P85’s voltage
2Add soldering or re-solder or replace U1501
3X-ray: check CPU and U1301’s soldering, re-solder or replace CPU
VIO18_PMU
C1502
U1501

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8. Side key FPC failure
Solution:
1Re-connect the side key FPC
2Replace the side key FPC and test again
3Check if VOLUME+/VOLUME-/KYPD_PWR_N ‘s voltage signal is normal
4X-ray: check CPU (Volume Key), PMIC U501 ’s soldering
5Add soldering or re-solder or replace CPU, PMIC
Side key Welding plate

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9. Cannot get charged, fail to identify USB
Solution:
1Check if KB connector is normal, re-connect or replace KB and test again.
2Check if KB connector J1806 is normal.
3Replace the battery and test again
4Replace the battery connector and test again
5Re-solder PMIC
PMIC
KB connector
Battery connector

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10. Rear camera function failure
Solution:
1Check if the rear camera is well assembled, re-assemble or replace the camera and again
2Check if the rear camera’s connector is damaged or poorly soldered, re-solder ore replace the camera
connector
3Check VREG_L10_2P8,VREG_CAM_AVDD,VREG_L6_1P8,VREG_L16_CAMDOVDD’s voltage
4Check FL1701,FL1703,FL1705,FL1707,FL1709 filter is damaged or poorly soldered
5Add soldering or re-solder or replace CPU
Rear camera connector
Filters

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11. Front camera function failure
Solution:
1Check if the front camera is well assembled, re-assemble or replace the camera and test again
2Check if the front camera’s connector is damaged or poorly soldered, re-solder or replace the connector
3Check VREG_CAM_AVDD,VREG_L6_1P8 voltage is abnormal, if abnormal, check if PMIC outputs abnormally,
or if the peripheral circuit has short/ open circuit
4Check if the front camera filter (FL1712,FL1713,FL1714) is damaged or poorly soldered
5Add soldering or re-solder or replace CPU
Front camera connector
CPU
Filters

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12.Flash failure
Solution:
1Upgrade SW and test again.
2Add 3.0V voltage at the two sides of LED welding plate, check if the LED can be lighten.
3Add soldering or replace Flash.
4Check if L1702 is open circuit.
5X-ray: check U1702 ’s soldering, add soldering and test again.
Flash
Flash driver IC

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12. Motor fault
Solution:
1Measure MOT+、MOT- magnitude of voltage and compare to normal MB’s
2Re-solder or replace the motor and test again
3Replace the motor connector and test again
4Re-solder or replace PMIC.
13. GSM network failure
PMIC
KB connector

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Solution:
1Check the welding status of the antenna on the KB board and contact with the antenna on battery cover, or
if the body is damaged.
2Check if RF connector is welding normal or open circuit
3Check if Front coupler U2001 is welding normal or is damaged.
4Check if the GSM (TX) - channel element is welding normal or is damaged;
5Check if the U2801 RF power amplifier chip is welding normal, and whether the relevant components are
damaged.
6Add soldering or replace U2801
7Add soldering or replace U1101
8Add soldering or replace CPU
14. CDMA network failure

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Solution:
1Check the welding status of the antenna on the KB board and contact with the antenna on battery cover, or
if the body is damaged.
2Check if RF connector is welding normal or open circuit
3Check if Front coupler FL2001 is welding normal or is damaged.

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4Check U2001 is welding normal or is damaged.
5Check Filter FL2305,,FL2315,FL2311 is welding normal or is damaged.
6Check if the crystal oscillator is normal.
7Add soldering or replace U2101,2102 or relevant component(L2300，L2310，L2322，L2317)
8Add soldering or replace U2801
9Add soldering or replace PMIC.
15. LTE network failure