Acer A315-41G similar to AN515-42, AC OK Battery OK but not charging

[mon2]

Flux the mosfet well and apply enough heat to make the component swim into place. Do not burn the part or the PCB in the process. After it is cool, be sure to check the resistance of the mosfet as usual (source - drain; source - gate; gate - drain).

[titomno2]

so I did it, checking the values everything unplugged and cold:
PQ305
LX_CHG -> UG_CHG => 19.59kOhms
LX_CHG -> +19VB_CHG => 1.6MOhms
UG_CHG -> +19VB_CHG => 2.7MOhms

PQ306
LX_CHG -> GND => 2.8MOhms
LG_CHG -> GND => 100kOhms
LG_CHG -> LX_CHG => 2MOhms

Still 0.000V on LG_CHG... when I plug the battery and adapter.
Still blinking amber right away... 🤔

[mon2]

Check the mosfets as follows. Remove all power. Meter in resistance mode.

Measure the resistance across the mosfet pins:

PQ305:

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

Post each measurement. Repeat for PQ306.

[titomno2]

PQ305
source & drain = 3.38Mohms
source & gate = 0.7 Ohms !!!
gate & drain = 5MOhms

PQ306
source & drain = 2.58Mohms
source & gate = 100kOhms
gate & drain = 3MOhms

[mon2]

PQ305 is certainly a suspect. Flux it well and remove while protecting any surrounding parts that may fly across the room. Also protect any plastic components.

Once the mosfet is off the board and cool to the touch, measure it again to see if the part is truly defective. It appears to be.

PS: Even PQ306 @ 100k ohms is a suspect. For mosfets, that is considered to be a low resistance measurement.

[titomno2]

Something is wrong with the board
I have 24MOhm or OL for each measurement on the mosfet cleaned twice just to be sure..
But on the board I have 19.44kOhms

[mon2]

Check mosfet @ PQ312 using the same method. Leave PQ305 off the board.

[titomno2]

PQ312 removed:
4MOhms between drain and source
OL between Gate and drain
OL between Gate and source

On the motherboard
Gate drain 4Mohms
Gate source 4.47Mohms
Drain source 5.27Mohms

So motherboard good and mosfet also

I have well cleaned with IPA both before measurement and short my probe each time to read the zero

[mon2]

What are the measurements now of the pcb pads (only) for pq305? Earlier you had very low measurements for that mosfet.

[titomno2]

Source to gate = 0.000Ohms at first then 19.56kOhms once I have measured between drain and source ! and after a while I measure 4.7 Ohms
Source to drain = 0.9MOhms (increasing)
drain to gate = 1.5Mohms

It is a strange behavior

[titomno2]

So If no new idea, I will solder back the component and maybe check for capacitor issue.
I have changed the ic chip, tested the mosfet separatly.
The remaining is may-be to swap the capacitor with another one.

[titomno2]

My last word after some extra work on the motherboard.
Following parts have been changed and all solder joint checked with camera:
PQ306 => changed twice has both from doner board were faulty (short circuit bewteen drain and gate).
PU301 => changed because I have burn it twice (my hands are shaking these days)
PR319 => changed as I have measured it at 3.9kOhms instead of 0Ohms (discovered after replacing PQ306 and PU301 because no POST).

After all these modifications:
Motherboard works with battery charged (from another computer).
Motherboard works with adapter.
Motherboard works whend retrieving adapter (and battery plugged in).
Charging is still not working (If I remove the battery windows indicate that pc is fully charged instead of not present => this is a new symptom).

Note that PQ306 on both motherboards (the one I tried to fix and the one used as doner board is not the same as PQ305, as everyone type 1306 were dead I use the same for PQ305 and PQ306 as it is indicated on the schematics.

I remain open to any advice that may be provided by anyone.

[titomno2]

So this is the last update and for a good reason. 😉
With the help of every one and especially mon2, I was able to solve issues one after the other.
So I made more deep research* and discovered even if the A315-41G motherboard is almost the same as the AN515-42, the battery used is not (it is a 2 cells AP16M5J).
Even if the BIOS is exactly the same version and the same for at least AN515-42 and A315-41G !!!
I have been fooled by my friend that have made the mistake to buy a wrong battery that works for AN515-42 AC14B8K 4 cells (but with exactly the same shape and same wiring !).
So I have buy a the correct one 2 cells on ebay and plugged in => works (great without adapter)
Once in windows level of battery indicated is 45% => Low but OK as the computer is powered properly.
Plugged in the ac adpater => heard a bip that I did not heard previously and amber lighted up right away and not blinking.
Check on the power supply => current draw is over 1.5 amps over the nominal consumption and thermal camera confirm the mosfets heating up (and not to much).
Now the level is 65% and increasing.

So for me this subject is closed and learn a lesson, never trust your friend (especially when he is not knowing what he his doing).

Have a nice evening and take care 😀

*deeper search also started as the keyboard mapping on A315-41G and AN515-42 is not the same also !