ASUS Zenbook UX433 DEAD

[corrize]

Hello, I have a Zenbook UX433. (No schematic nor boardview bur I have another same model, in working state tp compare).
It is dead : no light, nothing. And when I press power button : nothing. 19v is OK. I checked charging IC (battery removed) and the chip match ok but 3 flags are differents :

ACDET (pin6) UX433 good : 2.66v, UX433 dead : 3.1v
PROCHOT (pin10) – UX433 good : 5v, UX433 dead : 0v
TB_STAT (pin16) – UX433 good : 3.2v, UX433 dead : 0v

Do you know if it's bad or not pls ? (See below, the details of these flags)

I checked 3.3v-5v chip. It seams good. And I found 2 coils : with 3.3v and 5v (5.15v). So good.

But at the pins of BIOS chip, I can't find 3.3v, I found 3.1v (or lower, I can't remember). On the other working motherboard, I have 3.3v.
I wanted to check the continuity between the 3.3v bios pin and the provider
(coil or 3.3-5v chip). Because the 3.3v start but don't reach the bios pin, but that don't work. I thought it was just a wire between, but no. Not a good method.
What can I do after pls ?

*********
On the datasheet of charging IC :

ACDET Adapter detection input. Program adapter valid input threshold by connecting a resistor divider from adapter
input to ACDET pin to GND pin. When ACDET pin is above 0.6 V and VCC is above UVLO, REGN LDO is
present, ACOK comparator, input current buffer (IADP), discharge current buffer (IDCHG), independent
comparator, and power monitor buffer (PMON) can be enabled with SMBus. When ACDET is above 2.4V, and
VCC is above SRN but below ACOV, ACOK goes HIGH

PROCHOT Active low, open-drain output of the processor hot indicator. The charger IC monitors events like adapter current,
battery discharge current. After any event in the PROCHOT profile is triggered, a minimum 10-ms pulse is
asserted.

TB_STAT Active low, open-drain output for hybrid power boost mode indication. It is pulled low when the IC is operating in
boost mode. Otherwise, it is pulled high. Connect a 10-kΩ pullup resistor from TB_STAT pin to the pullup supply
rail.

[mon2]

Re: ASUS Zenbook UX433 DEAD

Post the full markings of the charger IC.

Measure the voltages of the mosfets near the charger IC.

update:

from searching your posted text, it is the TI # BQ24780S ?

ACDET (pin6) UX433 good : 2.66v, UX433 dead : 3.1v
PROCHOT (pin10) – UX433 good : 5v, UX433 dead : 0v
TB_STAT (pin16) – UX433 good : 3.2v, UX433 dead : 0v

1) Trace the ACDET pin to the local 2 resistors that create this voltage divider. Remove the power to the logic board. Meter in resistance mode (start with a high setting and lower it as needed to measure).

Then measure the resistor that will be between ACDET & the DCIN rail.
Repeat for the resistor between ACDET and ground. Together these 2 resistors lower the DCIN voltage (~19v raw from DC adapter) to a safe value.

Resistance for each resistor ?

Repeat for the known good logic board.

2) On the next 2 mismatches, these are OD (open drain pins). So they supply a logic low but not a logic high. Instead of the 'high' state, the pin will enter high impedance mode = floating pin. For this reason, there MUST be a local pull-up resistor present on each such pin. Likely they are there BUT the resistor must be connected to a pull-up voltage, like +3v3. Confirm this voltage rail for the working board and check that it exists on the non-working board. From the measured voltages, believe that rail is missing on the non-working board.

[corrize]

Re: ASUS Zenbook UX433 DEAD

I used current injection and found a small hot spot under die of chipset. The coil (at left above cpu/chipset) is shorted to ground, the same for mosfets close to this coil and same for some caps around and probably (can’t remember) caps under chipset. So all the chipset line is shorted to ground (0 Ohms).
This laptop was built in 2019, and thermal paste was completly dry and hard like a 10 years old laptop. Factory default.

Thanks for your help.

[ktmmotocross]

Re: ASUS Zenbook UX433 DEAD

i have here with me same UX431 with bad Intel CPU. nothing unusual

[corrize]

Re: ASUS Zenbook UX433 DEAD

have another same UX433, exactly the same, and same color, and it has a wet thermal paste too. Abnormal for 2019 factory product, maybe a bad serie.

[johnbeton]

Re: ASUS Zenbook UX433 DEAD

Seems like a problem with these models, I had the exact same problem with a UX433 a couple of weeks ago

[corrize]

Re: ASUS Zenbook UX433 DEAD

Today, someone else said he has same problem with UX433 ; thermal past dry and CPU/chipset dead. The owners of this model should replace the thermal past.