Asus x512ja suddenly no boot

[ss45]

Hi guys

Initially board wasn't able to turn on due to short on 19v and some liquid damage on the back side(keyboard facing side)

After cleaning and removing short it ran normal for a while able to boot into windows, ran some update.

Here is the kicker, for several times it would suddenly freeze. Initially force restart ING fixed that and the laptop would be able to boot again into Windows normally, after some runs would freeze again.

Until, suddenly it just hangs and unable to post anymore. orange charging light wouldn't turn on on plugging adapter and the battery amp is 0 (checked at shunt)

Good thing is at least power button responds.


I am kinda lost on what to do next
So appreciate the guide and direction

Maybe try to reflash bios ?

Thank you

[mcplslg123]

Re: Asus x512ja suddenly no boot

Should'nt be a bios issue IMHO. You mean charging LED is no more glowing?? If so thats a failure at an early stage of power plan. Check DC-in mosfets's gate and charging IC requirements to begin with.

[ss45]

Re: Asus x512ja suddenly no boot

You are right. Flashing bios didn't fix it.

Well I don't believe there is problem with MOSFETs since with adapter or battery the system can work and main rail has appropriate voltage, that is 19v if adapter only, or bat voltage if bat only.

Also no short found on all charging related mosfets.
With battery and adapter connected, voltage at battery terminal rise to 8.4, it's just that the current draw at shunt is 0

[mon2]

Re: Asus x512ja suddenly no boot

Mosfets can still be shorted.

Remove all power. Meter in resistance mode.

Check the resistance across

Source & drain
Source & gate
Gate & drain

Of each mosfet. Post each reading. Checking for low resistance = defective mosfet.

What is the charger IC on this logic board?

From the datasheet, can get a general idea of how the charging works.

Be sure the battery current sense lines are reaching the charger IC.

Can you post all voltages on the battery connector?

[ss45]

Re: Asus x512ja suddenly no boot

Oh the charger ic is good ol' humble bq24780

No short between gate and source nor drain source nor gate drain across MOSFETs driven by the charger ic

Voltage at battery terminal
red 8.3
green blue 3.3

Haven't check SCL SDA with scope yet

Charging is the least of concern for me, the elephant is that it doesn't post

I have never encountered laptop that wouldn't boot just because there is problem on charging circuit, have you ?

All voltages present, cpu, 3.3v, activity on bios cs di do clk pin. My guess is either dead on board ram or cpu

Time to move on I guess.... Thanks for the suggestion, really appreciate it !