Acer 5742G Power only on battery.

[mon2]

Re: Acer 5742G Power only on battery.

where are the highside and low side battery charger mosfet

PQ62 = high side battery charge mosfet
PQ64 = low side battery charge mosfet

These 2 mosfets essentially turn ON / OFF to dial up the desired voltage for the battery to charge. The charger IC closely monitors this voltage and the current consumed by the battery pack during the charge cycles to keep the process safe as to not start a fire, etc.

Are you using an official power adapter for this logic board or a lab adjustable power supply ?

Confirm the voltage of +RTCBATT.

[eukal]

Re: Acer 5742G Power only on battery.

Thanks again.
Here is the reading
Range in 200M
PQ62
1-2-3 = go from 0.42m to 0.90m and continue to up by 0.01m each 5-10 seconds
4 = oscilating 1.41m to 22m
5-6-7-8 = 2.66M

PQ64
1-2-3 = 00.01k this in range 2k
4 = go from 6M to out of range
5-6-7-8 = go from 0.42m to 0.90m and continue to up by 0.01m each 5-10 seconds


And i use an universal adapter but i can use an original acer adapter if needed.

For the +RTCBATT . Whitout adapter i have 0.120v ( for info the original rtc was desolder because no more voltage in it and i have buy another one, i wait it to arrived by post) And 3.108v with adapter plugged

[eukal]

Re: Acer 5742G Power only on battery.

PQ62 = high side battery charge mosfet
PQ64 = low side battery charge mosfet

These 2 mosfets essentially turn ON / OFF to dial up the desired voltage for the battery to charge. The charger IC closely monitors this voltage and the current consumed by the battery pack during the charge cycles to keep the process safe as to not start a fire, etc.

Are you using an official power adapter for this logic board or a lab adjustable power supply ?

Confirm the voltage of +RTCBATT.

Is the cmos battery required ?

[eukal]

Re: Acer 5742G Power only on battery.

I have continue to check why the laptop can boot with battery but no with adapter plug in and not with only adapter. So with only battery the gate of pq51 and PQ52 is at 12v so the 19v go to pq52 out whitout problem. If i plug the adapter or with the adapter only the gate saty a 18.84v so no 19v after pq52 but 18.52v.

I manage to check one more time PU18 because it was the part with water damage and i think i have found one problem. So the pin 5 have 4.8v (around 4.3v is awaited on this pin i have seen on other post) with the battery but soon i pluf the adapter the voltage drop to 2.4v and the laptop refuse to power on. I have 2.4v too with only the adapter. I have try to put 4.3v with my adaptable power supply and only the adapter no battery and wow the laptop power on whitout problem so now i'm sure the problem is here but i doesn't understand why. Have you ab idea ? Thanks

[eukal]

Re: Acer 5742G Power only on battery.

Continue checking, i have not the +5alw on pin 2 of PQ71 and if i plug 5v on it with adaptable power supply i can start the laptop.

[eukal]

Re: Acer 5742G Power only on battery.

SO i stop now to check because i think i have found the problem, there is a pad that are scrap on 3v/5v chip and i can't repair it, i have try with a tiny wire but no luck the chip become hot, i have try to swap the chip Rt8206b with TPS51427 i have on the other board ( it's the same) but same so i think there is another problem and now the laptop doesn't want to power on including with only the battery. Better luck next time. I hope this post can help another one. Thanks for your help mon2.