Asus Vivobook Pro 16X OLED No boot/Black screen

[Nyquistnoise]

Hi all,

Hoping to get some directions on a current repair of an Asus Vivobook Pro 16X. The laptop powers but shows no other signs of life, and appears to have all typical supplies according to boardview files (attached). Both CPU, GPU & PCH get sensibly warm & thermal camera reveals no obvious shorts. The only supply that makes me slightly wary is +1V8_AON_PLLVDD, as this measures 1V2. I believe this may be normal, however?

Pressing the power button gives you a lit keyboard & power/battery lights, but that's about it. No display (internal or external via HDMI) and eventually if you wait long enough, you get a 5 x slow white flash. I'd imagine this is an error code of some kind, but Asus reveals nothing as to what this means, so quite in the dark here.
If anyone has any ideas. I've got most repair gear available (irons, hot air, scopes, meters, programmers etc)

Boardviews were hard to get ahold of, so at the very least I hope this helps someone else! Boardview - https://www.badcaps.net/forum/troubl...1020-boardview

TIA,
Dan

[FriedFred]

Hi! This sounds to me shall be an "Always On" voltage and be always available, with and without battery, with and without pressing the power button, etc.
Do you have the other "Always On" voltages, like 3,3V and maybe 5V?
1.8V shall be between 1,75V and 1,85V.
There can be two problems with this:
a) The power supply IC has a problem and can not deliver 1.8V, just 1,2V. It can also be a problem with the resistor divider at the Feedback pin of this IC. Try to find a feedback voltage there, it should be 0,6V or 0,8V.
b) The "Client" of this voltage has a significant, but not full, short to GND.

You can also check the correct behaviour of this power supply chip, if you disconnect it from the outgoing power rail and measure the voltage then. There are usually some "solder bubbles" which connect outputs of power supply ICs with their corresponding "client" circuits.

[piernov]

"1V8" in the name if the net on the boardview does not necessarily mean the power rail has to be 1.8V.

[FriedFred]

This can be checked with the feedback voltage. if there is 0,8V or 0,6V, all is good and 1,2V is the correct voltage.