Asus Rog GL703G/Battery Connector Short

[reformatt]

Are you measuring across these components, or with one probe on ground?

As far as measurements go, small m is milli, large M is Mega. 6milliohms and 10 millohms appear to be across the current sense resistors, not resistance relative to ground.

[GlassMonolith]

reformatt I'm measuring everything to power connector ground. I haven't noticed if my meter is showing lowercase m, I think it's always M but I'll double check. **edit; Yes, it's all M**

Do i need to measure across both sides of the resistors though?

[reformatt]

Well none of that makes sense to me. You say that pin 1 of the battery connector (which should be your positive terminal) measures 0 ohms to ground, however it measure 6Mohms at the current sense resistor? They are connected together so should measure identically.

[GlassMonolith]

reformatt Measuring pin 1 again. Just to be sure, I've taken a photo and measured the end pin on both sides.

Far left: 5M ohm
Far right: 0.0 ohm

[reformatt]

So neither your main rail, nor your battery rail is shorted. So go back to mon's post #45, you need to check out your charger IC voltages. Likely based on what you did originally, you destroyed this IC.

Where this got derailed (for me anyway) is you put down your battery rail resistance to ground was 5 milliohms, but this proved to be 5 Megaohms 🙄.

[GlassMonolith]

reformatt Learning from my mistakes here. 😅 Can a multimeter even read milliohms, though?

Alright, so would you be able to elaborate a little better what Mon is asking? Being very very careful with fine tip probes, I'm measuring what pins with DC voltage?

[reformatt]

These are the main ones, expected values are adjacent if the chip was working correctly.

Pin 28 (Vcc) --> 19V or so with adaptor
Pin 24 (REGEN) --> 6V
Pin 5 (ACOK) --> 6V
Pin 6 (ACDET) --> 2.6V

Pin 4 (ACDRV) --> 25V

You can use a BQ24780S as a replacement for this chip, might even be what's fitted on the board instead of SN2867.

[GlassMonolith]

reformatt Honestly, I'm not even sure where these pins are supposed to be located.

I can assume different components, but which ones eludes my knowledge here.

[GlassMonolith]

I'll take all the photos you need if you're able to point them out for me.

[reformatt]

No boardview for this model unfortunately, but you can use the datasheet for the BQ24780S

https://www.ti.com/lit/gpn/BQ24780S

Page 3 has the pinout. There is a small dot on the chip to show where pin 1 is.

If you don't have the equipment or skills to replace a QFN IC I would highly recommend you send this board off to someone who does.

[GlassMonolith]

I'm confident in my ability with my hot air station enough to give it a shot. Otherwise, I think the price to have it dealt with might just be more reasonable to pay for a 2nd hand entire working board. But I prefer the challenge in the meantime.

That being said; I did find one single BQ24780S chip on the back side of the board. I looked over every QFN-looking chip I could find. Is that BQ24780S certainly the correct chip? (I have no idea if they're used for anything else) and I didn't find an SN2867.

[reformatt]

There is only ever one BQ charger chip in any laptop, it's not used for any other function. BQ24780S is the same chip functionally to the SN2867. They perform identically, just made by different manufacturers so have their own part numbers.

[GlassMonolith]

reformatt Okay, awesome. Now, I am curious, how the heck are these typically tested/metered? I have very sharp 1mm/0.2mm tip probes and even under magnification, this seems like it's gonna be a gamble to not jitter at all. Is there no way to bench test it out of circuit? Could I measure to the next component in the trace?

[reformatt]

You can measure off a component that is connected to that pin you want to measure. There is no boardview available, so you'll have to visually look at the tracks from each pin to work out what it connects to to meter off. I personally use the Mechanic P30 probes in conjunction with my microscope if I have to probe QFN's like that.

[GlassMonolith]

That was going to be my next question; could I measure to the nearest component/closer side on the circuit. I did notice that half the pins have nearby test pads too, so I think I should be able to knock this out pretty smoothly now.

[GlassMonolith]

reformatt Alright, got some positioning probes and here's what I have:

1: 0.02v
4: 0.02v
5: 0.02v
6: 2.6v
24: 1.2v
28: 19.0v

6 & 24 was measured to the nearest resistor end. Let me know if I need to measure anything more. I'll do every pin if needed.

[reformatt]

Pin 24 is your REGEN voltage, should be 6V. This is an internal linear regulator within the IC derived from Vcc (pin 28). The chip is very likely faulty.

[GlassMonolith]

reformatt Okay. Anything else I should check or test for further verification? Or just go straight to swapping out the QFN?

[mon2]

With no power, measure the resistance to ground of REGN pin. Need to check if there is an excessive load on REGN pin from perhaps the bulk cap on this pin. Post the resistance in ohms.

[GlassMonolith]

mon2 Pin 24 reads at 50.2ohms.