Zephyrus G14 GA401QM dead

[Ghostalker]

Hello I have an ASUS Zephyrus Laptop (Model GA401QM), bought on ebay and the previous owner claims he was using and the laptop stopped, He then tried to change battery and broke the connector on the battery and also on ripped a GND pad on the MB.

I was searching on internet and found two posts on this forum about a similar problem “ASUS ROG G14 (GA401) battery spark, dead.” and “Dead ASUS ROG G14 (GA401)” both by the user jacobtc.

I already made some measurements based on the “Dead ASUS ROG G14 (GA401)” post using GA401QM schematic provided here and Boardview provided here by user Stevedb.

Here is all I got so far:

- 1st DC Mosfet PQ8901 got voltages:
Drain = 20.36 Volts
Source = 0.166 Volts
Gate = 0.177 Volts

- 2nd DC Mosfet PQ8902 got voltages:
Drain = 4.36 Volts
Source = 0.100 Volts
Gate = 0.110 Volts

- Charger CI PU8900 (BQ24800) got voltages and resistances to ground (in this case with no AC charger of course):
ACDRV = 0.110 Volts and 7.35 MOhms
REGN = 0.287 Volts and 12.9 Ohms (this line seems to be shorted bipped on the continuity mode)
ACOK = 0.018 Volts and 100 KOhms
ACDET = 0 Volts and 197 KOhms
VCC = 19.85 Volts and around 3 MOhms

That’s all I did before trying to remove any component, inject voltage or use thermal camera.

[mon2]

Re: Zephyrus G14 GA401QM dead

I think your BQ24800 may be in trouble since it has VCC which is fed from the raw power adapter - perhaps OR'd with a dual common cathode diode with the adapter on one side / battery feed from the other side - whichever is the higher voltage will power this charger IC.

After the charger IC is powered, the internal LDO @ REGN should offer ~6 volts. It is not. Confirm that you are indeed on the proper pin for this device for REGN. Also, remove all power and check the resistance to ground of REGN. If the resistance is too low, the LDO will be unable to support the heavy load / heavy current and shut off. The thermal camera may reveal this.

Only if REGN works, then the ACDRV will follow = adapter voltage + REGN = ~25 volts. Then the 2*DCin mosfets will enable, unless they are leaky.

Do consider to carefully flux and remove the 4k resistor that is often in series with the ACDRV pin and the 2*DCin mosfet - gate pins. If one of the mosfets is defective, the ACDRV voltage will be absent.

You may need to replace the BQ24800 - should be available from Aliexpress (what isn't available over there?).

[Ghostalker]

Re: Zephyrus G14 GA401QM dead

Hi mon2, thanks a lot for the feedback. I'll remove the 4k resistor Friday and I'll post the results here.

Since Aliexpress products take more than a month to arrive here in Brazil, I'm planning to buy as much components as possible.

What should I buy? Charger IC, the 2 DC in Mosfets? Whatelse?

I wanna buy 5 of each in case some of them comes with defects.

Edit: Btw, Is it worth to connect the battery to check if the laptop boots? The battery is completly depleted so I'm thinking of "activate" it, but I don't know how many volts to inject nor the proper way to to this.

[mcplslg123]

Re: Zephyrus G14 GA401QM dead

Dont plug the battery at this stage. going by the resistance readings on REGN, it seems charger IC needs replacement. Look for a cap connected to REGN pin and remove it and then check resistance to GND on REGN again. If the resistance readings remain same,charger ic is very very likely bad. I dont see any point in removing the ACDRV resistor for now since REGN itself is missing,so there is no possibility of ACDRV working. Do check resistance between
Drain to source
Source to gate
Gate to drain for both dc-in mosfets. One of them may be faulty also.

[Ghostalker]

Re: Zephyrus G14 GA401QM dead

Heyas Mon2:

1 - resistance to ground of REGN is 12.9 Ohms and is beeping on continuity mode, I also removed a capacitor in the REGN line but capacitor is OK, the problem is the line.



2 - I suppose this the 4k resistor that is often in series with the ACDRV pin and the 2*DCin mosfet - gate pins?



I attached the pictures but for some reason I'm not seeing them here

[Ghostalker]

Re: Zephyrus G14 GA401QM dead

Hi mcplslg123:

I removed the capacitor (PC8912) But the capacitor is ok and the line is shorted.



I'm gonna remove the DC mosfets, tomorrow to measure the Source - Gate - Drain

[mcplslg123]

Re: Zephyrus G14 GA401QM dead

Yes, better to measure both dc-in fets so that you can order them(if needed) along with charger IC at one go.

[Ghostalker]

Re: Zephyrus G14 GA401QM dead

I can only find BQ24800 in China, but BQ24780 is avaliable, is it crazy to use it instead of BQ24800?

[mcplslg123]

Re: Zephyrus G14 GA401QM dead

BQ24780S should be used. Note the suffix "S". Its important. However, i"m not 100% sure whether BQ24780S and BQ24800 are inter chaneable or not. Some users claim success.

[Ghostalker]

Re: Zephyrus G14 GA401QM dead

BQ24780S should be used. Note the suffix "S". Its important. However, i"m not 100% sure whether BQ24780S and BQ24800 are inter chaneable or not. Some users claim success.

Hi my friend thanks for the answer, I'm just afraid if using this Q24780S or other wrong IC could be harmful to the laptop.

[Ghostalker]

Re: Zephyrus G14 GA401QM dead

Just a quick update, I ended up buying the exact CI and the 2 AC in Mosfets on Aliexpress, now I'll wait 1 month.

I'll post here news when I get the chips