ASUS vivobook X571 Shorts?

[revex666]

Goodday all of you,

I have an asus vivobook with some problems (i bought it broken), I'm new in the world of repairing motherboards, etc. i did some MOSFET and cap replacements and haven all the equipment, only not yet all the knowledge in faultfinding.

board: DAXKTDMB8C0 rev: C
The problem:
At first the laptop was not turning on at all and no lights.
I opened the laptop and checked if the adapter was working (it did). I found an exploded/missing capacitor and replaced it. The lights of the laptop turned on, but nothing was happening.
I replaced the battery (i red somewhere that there is a chance when the battery is too low it will not charge and the laptop will not start). And to my surprise, the laptop booted up just fine. I was quite pleased since it looked like an easy fix. However, after 20min the laptop died and would not power up again. I took it apart again and started measuring again. No power on the charger (but the light of the charging was on before).
So i started to just check some random caps and mosfets, since i can not find a schematic for this board. I did found a boardviewer file of an almost identical board to just help a bit.
What I found out:
- ADP-Detect pi is shorted to ground 0,3 ohm, is this logical or not? (i removed the adapter port to check if there was something wrong there but shorts where still present);
- VSS - Sense (PWM chip 968-ISL95880HRTZ) 3,5 ohms to ground
- VSSSA_Sense_R (PWM chip 968-ISL95880HRTZ) 2,6 ohms to ground
- capacitors on +VCC_Core line 2 ohm to ground ( i believe this is normal for the capacitors?)

Because I don't have a schematic I'm a bit stuck. What is my next step? is it already time to inject voltage somewhere (I really want to test my new thermal camera ).

 

[pcrepair]

Diagnosing a laptop motherboard without a proper schematic can be challenging, but here's a general approach you can consider based on the information you've provided:

1. Shorts to Ground: Generally, you shouldn't find shorts to ground on power input lines unless there's a problem. The ADP-Detect pi short to ground suggests there may be another component on that line that has failed. Similarly, for the PWM chip measurements you mentioned, it's tough to say without a schematic, but those could potentially be problematic as well.

2. Voltage Injection: Since you mentioned you have a thermal camera, you can indeed try voltage injection to locate the shorted component. But be cautious:

a. Start with a very low voltage (e.g., 1V) and current (e.g., 0.5A) to minimize risk.

b. Inject the voltage into the shorted line, and then monitor the board with the thermal camera. A shorted component will generally heat up very quickly.

c. Before attempting this, ensure that other critical components are isolated or protected. Some people use kapton tape or remove key ICs to prevent damage.

3. +VCC_Core Line: The resistance you mentioned for capacitors on the +VCC_Core line might be okay since capacitors tend to show low resistance to ground, especially if measured soon after power is applied. The real problem would be if they're shorted directly.

4. MOSFETs: They're a common point of failure. If you have a similar board for reference, compare resistance readings across similar points to see if they match.

5. Visual Inspection Examine the board under a microscope or magnifying glass for any signs of damage, discoloration, or anything that seems out of place. This is especially true for the components near the one that exploded.

6. Consider Professional Help: If you can't find the issue, it might be worth seeking out a professional who specializes in motherboard repairs, especially if the laptop has value or importance.

Always remember safety precautions when working with electronics. Avoid applying power to the board unless necessary, and always work in a well-ventilated area. If you're unsure about any steps or readings, it's better to ask or consult with someone knowledgeable before proceeding.