Asus FX505G - no power to battery and won't turn on

[CptChronic]

Hi,

My laptop won't turn on anymore, I am getting 20V from the charger into the first mosfet but there's no voltage on the source so nothing coming out the other side of the mosfet. So the battery isn't charging.

There are no shorts on either mosfets or anywhere else I can find. I've tried looking through the schematic but it makes no sense to me. The board view pdf is a waste of time too.

I took it apart earlier and had the board on the dwask, was poking around with the multimeter looking for shorts and then retested to see if voltage was getting to the battery port and it was. I had 12V on the red leads and 3.3 on the yellow and white. So I put it all back together testing each time I added something and it was fine until I added the battery. The 12V then dropped to 10V but then testing later I then get 0.3V on the 12V side of the battery port and nothing on yellow or white.

So I'm stuck, can anyone help please? Where should I be looking?

Some pictures here: https://imgur.com/a/D5DrFWe

Edit: I may of found something, this side of the mosfet is shorted to ground: https://imgur.com/a/X6R6jav

[Sephir0th]

Re: Asus FX505G - no power to battery and won't turn on

Remove power, measure resistance to GND here in Ohms mode and share the reading.

[CptChronic]

Re: Asus FX505G - no power to battery and won't turn on

Remove power, measure resistance to GND here in Ohms mode and share the reading.

It started in around 3MOhms and gradually dropped down to 94k

[Sephir0th]

Re: Asus FX505G - no power to battery and won't turn on

Edit: I may of found something, this side of the mosfet is shorted to ground: https://imgur.com/a/X6R6jav

Since this mosfet most likely belongs to the buck converter for the battery charging rail, it is probably the low-side mosfet. it is absolutely normal and expected to have one mosfet of a buck converter connected to GND, otherwise it could not create the down-stepped voltage. So I kindly ask you to stop doing random measurements.

Share close ups of the area around the DC-IN and Battery connector since we need to identify the charging controller.

Edit: Probably this one. Share the top marking please. And clarify why it does look so dirty there.

[CptChronic]

Re: Asus FX505G - no power to battery and won't turn on

Since this mosfet most likely belongs to the buck converter for the battery charging rail, it is probably the low-side mosfet. it is absolutely normal and expected to have one mosfet of a buck converter connected to GND, otherwise it could not create the down-stepped voltage. So I kindly ask you to stop doing random measurements.

Share close ups of the area around the DC-IN and Battery connector since we need to identify the charging controller.

Edit: Probably this one. Share the top marking please. And clarify why it does look so dirty there.

Haha my bad

I've got some closeups of the DC in and other places. Didn't see your message about that chip though so haven't got one as I'm at home now. I'll get the details on it tomorrow

I did notice the dirt on that chip when first looking, I'm pretty sure it's just dust, there's a bit more in other areas.

Here are the other pics: https://imgur.com/a/t1chL0t

[Sephir0th]

Re: Asus FX505G - no power to battery and won't turn on

The "dust" need to be ruled out anyway. So proper cleaning, share top marking and a nice and clear picture from the top of the IC with surrounding components please.

[CptChronic]

Re: Asus FX505G - no power to battery and won't turn on

The "dust" need to be ruled out anyway. So proper cleaning, share top marking and a nice and clear picture from the top of the IC with surrounding components please.

Sorry for the delay, just got in now. The chip is a BQ 24780S which is a battery charge controller, would make sense this thing is at fault. Datasheet here: https://www.google.com/url?sa=t&sour...Fj-GWLYsdvatqK

Pictures of the chip: https://imgur.com/a/6NIvyB8

Really appreciate your help so far buddy!

I'll get it all cleaned up now and test...

Edit: cleaned and reflowed the chip but am still only getting 0.3V on the 12V side of the battery port

[Sephir0th]

Re: Asus FX505G - no power to battery and won't turn on

Likely a issue around the charging controller or a faulty charging controller itself, yes.

Pictures were taken before or after cleaning(?), because it is still hard to identify the tracks with all this stuff in the picture. Angle and quality is perfectly fine, though.

You have sourced the datasheet, so start measuring voltages please. Pay attention to not short different tracks together. CMSRC, ACDRV, ACDET, ACOK, REGN and VCC

[CptChronic]

Re: Asus FX505G - no power to battery and won't turn on

Likely a issue around the charging controller or a faulty charging controller itself, yes.

Pictures were taken before or after cleaning(?), because it is still hard to identify the tracks with all this stuff in the picture. Angle and quality is perfectly fine, though.

You have sourced the datasheet, so start measuring voltages please. Pay attention to not short different tracks together. CMSRC, ACDRV, ACDET, ACOK, REGN and VCC

Ok I'll get to work on that, those pictures were before I cleaned it. Here's one from afterwards: https://imgur.com/a/xvNowuc

[CptChronic]

Re: Asus FX505G - no power to battery and won't turn on

Likely a issue around the charging controller or a faulty charging controller itself, yes.

Pictures were taken before or after cleaning(?), because it is still hard to identify the tracks with all this stuff in the picture. Angle and quality is perfectly fine, though.

You have sourced the datasheet, so start measuring voltages please. Pay attention to not short different tracks together. CMSRC, ACDRV, ACDET, ACOK, REGN and VCC

Not sure what I'm supposed to be comparing the voltages to in the datasheet, the names of the pins don't match the electrical characteristics, here's the voltages though: https://imgur.com/a/cc2bAXo

[Sephir0th]

Re: Asus FX505G - no power to battery and won't turn on

REGN is not up although VCC is above UVLO and ACDET present. Usually It points to a dead controller. But you should measure resistance to GND of all pins to make sure there is no unexpected short to GND somewhere. Measurements without power of course.

[CptChronic]

Re: Asus FX505G - no power to battery and won't turn on

REGN is not up although VCC is above UVLO and ACDET present. Usually It points to a dead controller. But you should measure resistance to GND of all pins to make sure there is no unexpected short to GND somewhere. Measurements without power of course.

The only pin connected to ground other than ground is pin 15 BATPRESS - Active low battery present input signal. Low indicates battery present, high indicates battery absent. The device exits the LEARN function and turns on ACFET/RBFET within 100 µs if BATPRES pin is pulled high. Upon BATPRES from LOW to HIGH, battery charging and hybrid power boost mode are disabled.

I'm guessing low is 0V but as the battery isn't present it should be showing as high?

I've just removed the chip and it's still linked to ground on that pin

[Sephir0th]

Re: Asus FX505G - no power to battery and won't turn on

The only pin connected to ground other than ground is pin 15 BATPRESS - Active low battery present input signal. Low indicates battery present, high indicates battery absent. The device exits the LEARN function and turns on ACFET/RBFET within 100 µs if BATPRES pin is pulled high. Upon BATPRES from LOW to HIGH, battery charging and hybrid power boost mode are disabled.

I'm guessing low is 0V but as the battery isn't present it should be showing as high?

I've just removed the chip and it's still linked to ground on that pin

All good. Some manufacturer pull this line to GND by factory. So most likely no issue here. My suggestion ist to replace the BQ24780S.

[CptChronic]

Re: Asus FX505G - no power to battery and won't turn on

All good. Some manufacturer pull this line to GND by factory. So most likely no issue here. My suggestion ist to replace the BQ24780S.

Perfect, I've got a chip ordered and will update you once it's fitted. Thank you so much for your help, have a great weekend

[Sephir0th]

Re: Asus FX505G - no power to battery and won't turn on

Do it and share pictures of your job to rule out a "technician induced" issue. Don't worry but these controller are sometimes hard to solder. Good luck.

[CptChronic]

Re: Asus FX505G - no power to battery and won't turn on

Do it and share pictures of your job to rule out a "technician induced" issue. Don't worry but these controller are sometimes hard to solder. Good luck.

Bad news buddy, it's exactly the same 🙁
I've done a few of these chips before on xbox's so am not too bad with them. They are a pain though at times. Couple of pics here: https://imgur.com/a/wf6SON7 I've got an endoscope attachment for my microscope so have checked all the solder connections and they're good.

[Sephir0th]

Re: Asus FX505G - no power to battery and won't turn on

Share the voltages you get at VCC, ACDET, REGN and ACDRV

[CptChronic]

Re: Asus FX505G - no power to battery and won't turn on

Share the voltages you get at VCC, ACDET, REGN and ACDRV

20.10V at VCC
2.766V at ACDET
6.047 at REGN
2.546V at ACDRV

So that has made a change actually. Still only getting 0.227 at the battery connection though

[Sephir0th]

Re: Asus FX505G - no power to battery and won't turn on

ACDRV is low, but not without voltage. Could point to faulty DC-IN Mosfets. Do you know howto check? Sadly we didn't this sanity measurements before...

[mon2]

Re: Asus FX505G - no power to battery and won't turn on

2.546V at ACDRV

Remove the ~4k resistor that will be in series with the ACDRV pin and often is driving the gate pins of the 2 x DCin mosfets.

Do not lose the removed ~4k resistor.

Power up again. What is the voltage to ground now of the ACDRV pin?