Acer Swift 3 SF314-52-P987 dead

[dicky96]

Hi guys I have this Acer Swift SF314-32

It's quiet a nice laptop with SSD

It is completely dead. The battery is completely flat. I connected my bench PSU to the laptop - I have 19V going in (measured on the motherboard where the coaxial power connects) but it draws no current according to my PSU

It looks like the 19V goes via a couple of low value resistors in parallel (on the back of the board) to the resistor marked 2R2 near the power connector and the first of the two FETs. But no voltage is going further than that

I've seen Sorin on youtube just shorts out the FET to see if it will power up. That always seems like a botch job to me but I'm open to suggestion

Any other suggestions?

Anyone have schematics or boardview for this?

Cheers

[Techtiger]

Re: Acer Swift 3 SF314-32 dead

What is the voltage on the 1st 2 fets all pins & R010? To check if it’s working or not charge the Battery with the Bench PSU & power it &see

[dicky96]

Re: Acer Swift 3 SF314-32 dead

cheers TechTiger that sounds sensible

Rather than check the FET voltages as the laptop is in bits at the moment I tried to charge the battery - but it isn't drawing any current from my bench PSU.

I set current limit to 1A and started with 15.2V and increased that to 17V and expected the charge to kick in like with a car battery but it doesn't

The battery (off load) reads 0.02V

I tried apply the bench PSU across the red and black wires - do I have to do something with the other coloured wires to charge it? see pic. The resistor isn't doing anything electrically (it's 4M7) it's just there so I can connect the crocodile clips to the battery connector. I do have a good connection to the battery by the way, I checked.

[SMDFlea]

Re: Acer Swift 3 SF314-32 dead

You sure SF314-32 is the right model number. You can`t charge the battery with just the red,black wires.Test the two DC in mosfets first

[dicky96]

Re: Acer Swift 3 SF314-32 dead

Sorry my mistake
SF314-52-P987

[dicky96]

Re: Acer Swift 3 SF314-32 dead

OK so with the power attached to the motherboard and the keyboard ribbon attached (as the power switch is on the keyboard) I get 19V going in to the first FET but a fluctuating voltage on both the gates and the voltage on the output from the first FET goes from 0V to a small negative maybe -0.05V with each pulse

What I am actually seeing - and it is only possible to see it on the scope, is a narrow pulse about 6V high maybe once a second on both FET gates and another narrow pulse less than 1V high on the output (Drain) of first and second FET. On my bench PSU I see the current meter flicking to maybe 50-60mA (not on every pulse) and oddly the CC led is flashing extremely dim/breifly and the voltage would sometimes drop to around 18.8V too. This happens even if I wind the current limit up to the full 3A

At first I thought there was something wrong with my bench PSU but there isn't

I had a quick look and I have a dead short to ground on the output (Drain) of the second FET

https://pdf1.alldatasheet.com/datash...M4387NSKP.html

The 6V pulse on the gates is very narrow and it looks like they turn off again so quickly my bench PSU just about has time to go into CC mode and the current meter can't display the actual current.

So that obviously is why the laptop is dead. There is a short to ground on the 19V rail somewhere after the second FET.

I can see a couple of buck regulator coils so I checked for shorts there as well but they read OK

[SMDFlea]

Re: Acer Swift 3 SF314-52-P987 dead

Posted a schematic,not sure if its the right one. https://www.badcaps.net/forum/showthread.php?p=992196 .If you`re injecting voltage on the 19V rail, use 1V 1A.

[Techtiger]

Re: Acer Swift 3 SF314-32 dead

OK so with the power attached to the motherboard and the keyboard ribbon attached (as the power switch is on the keyboard) I get 19V going in to the first FET but a fluctuating voltage on both the gates and the voltage on the output from the first FET goes from 0V to a small negative maybe -0.05V with each pulse

What I am actually seeing - and it is only possible to see it on the scope, is a narrow pulse about 6V high maybe once a second on both FET gates and another narrow pulse less than 1V high on the output (Drain) of first and second FET. On my bench PSU I see the current meter flicking to maybe 50-60mA (not on every pulse) and oddly the CC led is flashing extremely dim/breifly and the voltage would sometimes drop to around 18.8V too. This happens even if I wind the current limit up to the full 3A

At first I thought there was something wrong with my bench PSU but there isn't

I had a quick look and I have a dead short to ground on the output (Drain) of the second FET

https://pdf1.alldatasheet.com/datash...M4387NSKP.html

The 6V pulse on the gates is very narrow and it looks like they turn off again so quickly my bench PSU just about has time to go into CC mode and the current meter can't display the actual current.

So that obviously is why the laptop is dead. There is a short to ground on the 19V rail somewhere after the second FET.

I can see a couple of buck regulator coils so I checked for shorts there as well but they read OK

As you know 6V on Gate N-channel will not bypass the voltage above 22-28V will turn on the fet , near the second fet you have the CLR R010 what is the Resistance to GND if +19V is down to GND take a wire sold it to CLR +1.5V 3A will heat up the any bad component but before you go futher make sure 1st 2 fets are ok test ohms on those 2

[dicky96]

Re: Acer Swift 3 SF314-52-P987 dead

This one is fixed

It was a MLCC capacitor near the buck regulators under the metal sheilding. Located by sending 3A of current into the 19V rail after the two FETS and waiting for something to get hot

[mobotest]

Re: Acer Swift 3 SF314-52-P987 dead

Is your laptop functional again?
If it is functional, does the inductor involved in charging the battery get hot to touch while battery is being charged?

If schematic in post #7 is correct for your board, then L8800 is the battery charging inductor.

[dicky96]

Re: Acer Swift 3 SF314-52-P987 dead

Hi mobotest

Yes it was functional after removing the short circuit capacitor, both with the charger attached and on battery only.

I gave it back to the owner the same day I posted here (so I could not check for the hot inductor) and he is using it for his work so I am sure it has not failed again.