Asus ZS551KL User manual

ZS551KL
EE Troubleshooting Guide
Introduction & Training
2017/8/9

ZS551KL Outline
•Component and PCB Board Introduction
•Power On Sequence
•BL Troubleshooting Guide
•ASSY Troubleshooting Guide

PCB Board Introduction (TOP)
P-Sensor
SIM2/SD/SIM1
CAM ISP
MSM8998
LPDDR4x
UFS
Indicator LED
Receiver
Speaker
AMP
Receiver
AMP
NFC IC PMI8998 OVP IC
USB
Switch
ADC

PCB Board Introduction (BOTTOM)
PM8998
RCAM &
G+G CONN
FCAM
CONN
Side key
CONN
PM8005
LCM
CONN
WCD933
5
SMB138
1
BATT
CONN
B2B
CONN
Vibrator
AMP
LCM
driver
RGB
laser
Laser
sensor
Flash LED
MIC3
MIC3
Ecompass

SUB Board Introduction (TOP)
USB_TYPEC_CONNHall sensor
Vibrator
springs

SUB Board Introduction (BOTTOM)
Audio jack
CONN
USB_TYPEC_CONN
Fingerprint
CONN
B2B
CONN
PU3302
Main MIC

ZS551KL Outline
•Component and PCB Board
Introduction
•Power On Sequence
•BL Troubleshooting Guide
•ASSY Troubleshooting Guide

POWER ON SEQUENCE

ZS551KL Outline
•Component and PCB Board
Introduction
•Power On Sequence
•DL/BMMI Troubleshooting Guide
•ASSY Troubleshooting Guide

1001 Provision check fail-DL
PC can’t detect USB COMPORT. Check your device manager for COM Qualcomm
QDLoader 9008. If not, please check:
1. Check the power supply/battery (4.2V)
2. Make sure all fixture pins contact well, also check the connection of the IOFPC
and Sub board
3. If heavy current occurs when booting up, probe VBAT (T9603 or T9602) and
VPH_PWR (C2402.1 or C2402.1) and search for short circuits.
(1) VPH_PWR shorts to GND: X-ray check PMIC PU9701 & PU8401 & PU9001,
NFC Power U5402, BL driver PU8901, Audio codec AU2601, Vibrator AMP
U2401.
4. If system shuts down before booting up, check MSM_RESIN_N (T8702) if the
TP is high (1.2V). Check which power in the PON sequence ended.
(2) VREG_S2A, S8A, S9A, S3C abnormal impedance: Check both DDR &
MSM(U0201), PMIC(PU8401, PU9701) to search for short circuits. If not, try to
reheat or remount DDR.

1002 UFS provision fail -DL
UFS provision fail
1. Please open the device manager on the PC and retry offline. Monitor QDLoader
9008 remains or not when provision. If not, check your power supply/battery,
and the power key status (T2503).
2. If retry fail, try to burn QFIL lite image (ask BSP). If success, we can narrow down
to DDR problems. Check by X-ray.
3. If LITE image fail, check UFS (U1101) and surroundings. Reheat U1101 or
change the UFS.

1004 DL image fail -DL
Flash Factory image fail often known as SMT problems.
1. Monitor the current before/after flash image.
2. If there is heavy current, check CPU/DDR (U0201) and UFS (U1101) to search
for SMT problems.
3. If no SMT problems found, demount the shielding on the backside of the CPU.
Check the power on sequence to check power rails below:
(1) C0711.1 (VREG_S4A_1P8)
(2) U0737.1 (VREG_S2A_1P125)
(3) U0813.3 (VREG_S3C_0P6)
(4) U0806.1 (VREG_S8A_0P8)
(5) U0916.1 (VREG_S9A_0P8)
If power on sequence ended at power rails above, try to remount DDR.

401 Boot up issues-DL/BMMI
1. Download: ADB not found during reboot after flash image.
(1) Check the voltage of the power supply (4.2 V), and monitor the current when
power on key pressed down.
(2) Check both fixture pins’ contact (T9613 & T9606)
(3) Open the device manager and test offline with a panel connected. If the panel
blackouts when showing ASUS log, please check the connection between
IOFPC & SUB board. If it blackouts when showing android logo, please enter
fastboot mode and run cmd.exe:
fastboot erase modemst1
fastboot erase modemst2
fastboot erase fsc
fastboot reboot
If the device enters home after reboot, check RF defects using X-ray.
2. Board MMI: Equipment, key part installation that cause boot fail.
(1) Change the power supply into manual, then press power on. Monitor the
current to see if it enters home.
(2) If testing the MB, swap IOFPC/SB; If testing SB, please change MB.

No display-BMMI
Display blackout after a flicker, or just no display while ADB device can be
recognized after booting up.
1. Check CON1602 for any short circuits, shift, or solder skips.
2. Swap the testing panel and also check the connector on the panel FPC.
3. Check PU8901, PC8904, PC8905 by X-ray and search for any short circuits, or
SMT issues.
4. If nothing found using X-ray, demount shielding to check PU8901, PC8904,
PC8905 for defects on IC or any short circuits .
5. Probe the power net VDISP_P_OUT、VDISP_M_OUT、VREG_WLED and
compare the impedance with normal PCB
6. Probe the power net VDISP_P_OUT(+4.6V)、VDISP_M_OUT (-2.5V) 、
VREG_WLED (+6.1V). Change PU8901 if any power with a different voltage.
[Check the SMT to see if any solder skips]

724 SIM test fail-BMMI
Check R2212 for SMT issues, and probe the detect pin’s C2212.1 status shown
below.(1.8V)；
If detect pin is high when tray inserted (normal),
1. Probe SIM1 power VDD_SIM(1.8V) or SIM2 power VREG_L10A_1P8 when either
SIM inserted. Check U5401、PU8401 for any defects if any power unusual.
2. Compare the impedance of UIM1_CLK、UIM1_RESET、UIM1_DATA[SIM1] or
UIM2_CLK 、UIM2_RESET 、UIM2_DATA[SIM2] to normal PCB.
3. If any unusual impedance issue, reheat PoP; If still NG, demount PoP and probe
the signal to check any open circuits (check each net).
4. Remount the PoP if no open circuits.

824 SDCARD test fail-BMMI
1. Probe the detect pin’s status (same as SIM fail)；
2. Probe SDC2_VDD_CON C2208.1. Monitor the voltage when SD card inserted.
(2.95V for few secs and back to 0V)
3. If 2. fails, check the appearance of U2201 to find any cracks, SMT issues, and also
check inside the tray shielding to find any bent or shifted pin. Change U2201 or
repair the parts.
Green net is SD_CARD_DET, yellow net
is SDC2_VDD_CON. Check all
surrounding components.

835/853 Ecompass test fail-BMMI
U1802 E compass can’t initial, or I2C bus error. Please check:
1. Check the appearance of U1802, C1809 for cracks, short circuits, wrong polarity.
Change U1802 if any defect found.
2. If no defect found, probe U1803 4 pins and compare the impedance with
normal PCB. [check if any short circuits between each pin]
3. U1803.B2/B1/A2 voltage should be 1.8V(B2 / A2 are I2C SDA/SCK)
4. X-ray and check both R0407,R0408 for SMT issues.
5. Swap U1802 to check the IC.
U1802
C1809

931、932、907、908、994 MIC Fail - BMMI
There are three MICs on the device, including on the SUB board AU3401(Main Mic),
and also main board AU2701(2nd Mic)、AU2704(3rd Mic). These error code means
Board_Mic_FREQ Fail or Board_Mic_Volt Fail
1. Check the appearance of all MIC for wrong polarity, shift, and solder overflow.
Besides, also check surrounding components.
2. If all MIC appearance are normal, check the MIC through the hole using a
microscope to check any foreign matters or cracks on the film for
Board_Mic_FREQ fail.
3. If Board_Mic_FREQ PASS but Board_Mic_Volt Fail, the fixture and equipment
need to be tuned.

950/986 TYPE C test fail-BMMI
USB can’t connect through one specific side of the TYPE C connector.
950-Main board:
1. Swap both Sub board and IOFPC to sort out the fault part.
2. Probe both TYPE C CC pin’s (T1704 and T1705) impedance to GND (normally
2M Ohm). Both pin’s voltage should be switching instead of one high level (3V)
and the other low level (0V) when power on.
3. Check PQ9001, PQ9002, PQ9003, PU9502 by X-ray to find any short circuits,
solder overflow, or IC cracks.
4. Check PQ9001, PQ9002, PQ9003, PU9502 to find any SMT issues by demount
the shielding above.
986-Sub board:
1. Check TYPE C connector if there are any SMT issues (pin shift, solder skip)
2. Check CON3201 and find any sunken pins, matters, or cracks.
3. Check the USB TYPE C connector for any internal solder skip, short circuits by X-
ray.

996 LID test fail-BMMI
LID apk passed, but LID test fail.
1. Use x-ray to confirm all components in the picture are mounted, or demount
the shielding (the one with CPU & UFS) and check are there any lost
components.
2. Demount the shielding and check the appearance of PQ8004, PQ8005 and their
surrounding components (wrong polarity, IC cracks, short circuits)
3. Check the impedance of net LID_EN、USBCON_LID (with key parts), and
compare with normal PCB.
4. If the impedance seems normal, please connect the SUB board and USB cable
to power on and check the net voltage of LID_EN、USBCON_LID. If both nets
are high level(1.8V), please change PQ8004.