Asus UX582Z no longer charges the battery

[orasl]

Hi Super BADCAPS :-)
Today i have a challenge... New Asus UX582Z laptop with 2 screen.

The motherboard is well powered and the charger is not in a short circuit. Before the computer no longer turns on, it no longer charges the battery, then once the battery runs out, the computer obviously does not turn on anymore.
I noted several voltage points on the motherboard, but it seems that at the battery charge output the voltage is not correct.
I have the impression that a mosfet does not open a few times because it lacks power on the main one while the power is ok on the rest of the motherboard.

The computer’s motherboard is UX582ZS and attached are some photos and some photos with voltage annotations.
I tried to follow the methods of your forum to eliminate possible defects of the motherboard, but without result.

Do you have an idea?

Thank you and have a nice day

[mon2]

Review the mosfet near the DC adapter connector. Remove all power. Meter in resistance mode.

Measure the resistance across this mosfet:

source (1-2-3) & drain (5-6-7-8)
source & gate (4)
gate & drain

Post each measurement. Each such measurement should be hundreds of k ohms or higher else is likely to be defective.

[orasl]

Hi from france Mon2
and thank you for your help ! it is really very appreciated.
The mosfet next to the DC adapet connector is PKCH2BB

For source & drain measurement is 507 Ohms << defective ?
source & gate 28 Ohms
gate & drain 43 Ohms

He might be the culprit!

do you think I order this : https://www.ebay.fr/itm/365577747159...Bk9SR9it5sqoZw

[mon2]

Yup! Waaaay too low of resistance values. Any chance you have an old motherboard at your disposal? This is a jellybean N-channel mosfet. If you can find the very common 5x6mm device on another motherboard, confirm it is N-channel and swap this part out.

Also suggest to test the resistance to ground of each of these pins. That is, we want to confirm that there is not a shortd part downstream that caused this mosfet to become defective. From our experience, the branded mosfets are of higher quality than offshore generics used by motherboard companies. For example, the TI mosfet is a good choice but certainly hunt for old donor motherboards. The actual part number is not important but higher the current support (ie. low Rds value) - the better.

Recommend to flux and remove this part. Allow it to cool down. Then measure the same pins while the mosfet is on your work bench. Suspecting that the measurements will remain low = mosfet is defective.

While this part is off the board, proceed to test the resistance to ground of the pcb pads for this part. Checking if there is a short downstream.

[orasl]

Wait , I think there's a mistake in my measurements... I'm using the LCR-ST1 (https://www.fnirsi.com/fr/products/l...zG1M5loT2rYbrA), but I've just tested it again and the readings are completely different... I'll try another tester
Thanks for the advice. I'll give it all a go and let you know how it goes tomorrow. That's really kind of you.

[orasl]

Hi mon2, i hope today your are fine !
I have found mosfet N-channel on old motherboard and i have swap this. No result :-(
Before swap I tested it as you said, once the component was removed, checking the component's contacts on the motherboard and ground, and there's no short circuit.

I measured the removed component; here are the values. It seems to be faulty, though.
Perhaps I'm not measuring correctly with the tester?

[mon2]

Your meter is the manual select type.

The 89k2 ohms = 89.2k ohms is considered to be very low for a good mosfet so we can assume that this mosfet is defective. You can try reversing the meter leads but likely this value will remain low.

The tests with the '1' = OL = over limit for the selected meter scale. You are on the 200k ohm scale but the measurement is > 200k ohms so the meter shows the '1'. Proceed to switch to a higher meter scale and you should have a valid measurement. Either way, the 89k ohms is showing that his mosfet is defective.

Repeat the same test with the new mosfet you have soldered onto the board. Respectively, nearby the new mosfet, there will be the 2nd DC in mosfet. Often there are 2 x DCin mosfets in the power path. Some have 4. Assuming that you have 2 in this region, repeat the same tests on the 2nd DCin mosfets.

Nearby these mosfets will the battery charger IC. Share a pic of this IC so we can study which design is onboard. As per the charger sticky article by piernov, the DCin mosfets are the key suspects.