ASUS G14 GA401QM Charge Light w/ No Power On

[ResoluteHawk]

Re: ASUS G14 GA401QM Charge Light w/ No Power On

Yes initially when plugged in Pin 1 on R3033 is 3.362V and pressing the button button drops it to around 3.2V but then it goes back up.

Just to make sure the power button yields a response, if I hold the power button down for 20 seconds while plugged in, the voltage drops to 0 and almost instantly goes back up to 3.362V but the orange charge light turns off.

[Sephir0th]

Re: ASUS G14 GA401QM Charge Light w/ No Power On

Okay, it seems the logic requirements are met to start the board. however, before digging to deep, overview of the present voltages and resistances to GND please: PL8301, PL8401, PL8701 and PL8702

To not miss a partial short to GND or similar.

[ResoluteHawk]

Re: ASUS G14 GA401QM Charge Light w/ No Power On

PL8301 => 0.757V and 60 Ohms
PL8401 => 1.84V and 613 Ohms
PL8701 => 5.1V and 346 Ohms
PL8702 => 3.36V and 3.54K Ohms

[Sephir0th]

Re: ASUS G14 GA401QM Charge Light w/ No Power On

It is a important lesson, to not overlook the simple things before digging to deep and get lost this way.

So I suspect a partial short at the 1.8V and at the 5V rail. However, the short of the 5V rail is more clear but still not low enough to have much current draw.

For the next step you need a bench top PSU and a thermal camera

[ResoluteHawk]

Re: ASUS G14 GA401QM Charge Light w/ No Power On

OK I have both. Yeah shoot I don't know how I missed doing this step but the below did contribute to it.
I typically don't inject voltage unless it's a dead short. Low resistance usually never has any results with voltage injection.

Here's the weird thing. When I measured the 1.8v coil in resistance mode, I got the 613 Ohms. I had to move my hand though so I took the probe off and then put it back on the coil. When I did, it measured 1.9K Ohms. When seeing if I could replicate it, I found that I could do this multiple times and the same thing always happened.

The 1.8v rail is the only voltage rail that exhibits this behavior. I've made sure it wasn't my multimeter probes by trying different probes and the same thing happens. Every other voltage rail has a constant resistance measurement.

[ResoluteHawk]

Re: ASUS G14 GA401QM Charge Light w/ No Power On

So I injected 1V at 1A into the 1.8V coil (PL8401), and I noticed a heat spot coming from PU8401. I looked at the rest of the board but no other heat spots are present; not even on the CPU.

Just to make sure the correct voltage was present, I then upped the voltage to 1.8V which is supposed to be present on the coil and still PU8401 was the only spot getting warm. Board was drawing 1A at 0.78V and PU8401 was at 100-110 degrees F.

CPU still didn't show any heat spot with 1.8V.

[Sephir0th]

Re: ASUS G14 GA401QM Charge Light w/ No Power On

Okay, you're likely on something. However, if I remember correct I have advised to check the 5V rail first since the 1.8V rail was inconclusive in my opinion.

[ResoluteHawk]

Re: ASUS G14 GA401QM Charge Light w/ No Power On

Ok, so if I inject 1V into the 5V coil (PL8701), PQL8701 gets warm. Resistance from Drain to Source on this is 300 Ohms; taking it off the board and the resistance at the 5V coil goes up to 4.5K Ohms. Measuring the MOSFET in resistance mode from Drain to Source after taking it off and letting it cool yields ~350 Ohms so I think this needs to be replaced as that is way too low.

I also have working board that I just got today. Tested this one and the resistance on the 1.8V rail is 2K Ohms. That sounds like more of a healthy value. 5V rail is ~4.8K Ohms.

If I do the exact same thing with injecting 1.8V at the same amperage on PL8401, the same IC (PU8401) gets warm, and it still draws 1A at 0.78V but the board works and posts and I get into Windows and everything is recognized without issues.

[ResoluteHawk]

Re: ASUS G14 GA401QM Charge Light w/ No Power On

New development. And this is just strange. I thought we had a clear fault with either the EC or PCH, or both. SUSB# and SUSC# were never present.

I don't know how many times I plugged in this board but today I thought I would take some measurements around the EC in voltage and resistance mode and compare them with a working board.

When I plugged in power, the board started and fans started spinning, as well as the white power led coming on. It got all the way into the BIOS as well.

In the words of Sorin from Electronics Repair School: Proper Weird.

[Sephir0th]

Re: ASUS G14 GA401QM Charge Light w/ No Power On

Maybe a intermittent issue with the +5VSUS buck converter. It might appear again soon.