Asus Rog GL703G/Battery Connector Short

[mon2]

Numerous issues.

1: 0.90v - ACN ; no power from the external power adapter (should be ~19v)
2: 0.90v - ACP ; no power from the external power adapter (should be ~19v)
3: 0.08v - CMSRC
4: 0.08v - ACDRV ; should be ~25 volts under normal conditions
24: 0.02v - REGN ; should be ~6 volts under normal conditions
28: 19.5v - VCC ; ok

Remove all power. Meter in resistance mode. Measure the resistance to ground of pin # 1 on the charger IC = ACN. What is the resistance? We are checking if the main power rail is shorted or not.

The charger IC may need a reflow but wait till we see the measurements.

In general - Suggest to flux and reflow the charger IC till the IC swims into place onto the logic board.

[GlassMonolith]

Resistance on Pin 1: 4-5Mohm

[mon2]

Ok. So no short on the main power rail - good. The guilty parties are most likely the 2 x DCin mosfets (as per the textbook by @Piernov's sticky on the charger circuits).

Locate the mosfets @ PQ8901 and PQ8902. If either is shorted (most likely) - the game stops.

Remove all power. Meter in resistance mode.

Measure the resistance across the mosfets as follows:

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. Check both mosfets. We are checking for a low resistance which usually means the mosfet is leaky. Once this occurs, the charger IC will power off the DCin mosfets which enable through the ACDRV pin using a boosted voltage of ~25v.

[GlassMonolith]

I'm a bit lost reading schematics, nor do I actually have them. Where would PQ8901 and PQ8902 be located? Are these the ones you had me test far earlier in this post?

[mon2]

I think so but here are their locations again.

Locate the dimple on the topside = pin # 1. Then proceed to measure as above but only with the power off. Provided the charger IC is soldered in ok, the ACDRV voltage should be ~25 volts unless one of these mosfets is defective. Often, the 2nd DCin mosfets is the bad one but test both.

[GlassMonolith]

Okay, these got a little confusing because I ended up with different measurements going over them a second time to verify.

(1st time);
PQ8901
S+D: 0.0Mohm
S+G: 4.7Mohm
G+D: 4.7Mohm
PQ8902
S+D: 0.0Mohm
S+G: 4.7Mohm
G+D: 11Mohm

(2nd time);
PQ8901
S+D: 5.0Mohm
S+G: 4.7Mohm
G+D: 11Mohm
PQ8902
S+D: 5.0Mohm
S+G: 4.7Mohm
G+D: 11Mohm

[mon2]

PQ8901
S+D: 5.0Mohm
S+G: 4.7ohm

I think you mean 4.7Mohms? If they are Mohms - the readings are ok. More concerned then if the solder connections are mating on each PCB pad.

Remove all power. Measure the resistance to ground of the REGN pin on this charger IC. We are checking if there is a short on this line.

Flux the IC and reflow the part with enough heat to melt the solder and allow for the charger IC to swim into place. Apply the hot air tool in circles over the charger IC to keep each area of the part heated.

I think the very first check should be to rework the IC till you have the REGN pin @ ~6 volts. This is fundamental and works by taking in the ~19v and lowers it to 6 volts = LDO regulator. Simple. Since we do not have this - review the soldering / review that pin # 1 of this new IC is where it should be.

PS: Just reviewed your topview soldering and your pin # 1 is correct on the board. Need to still review if there is enough solder on each pad so flux and reflow it. Low air pressure so the tiny parts nearby do not go flying across the room.

[mon2]

With no power -> what is the resistance to ground of the REGN pin on this new replacement? Earlier you had ~50 ohms to ground which to me was too low.

[GlassMonolith]

Yes, sorry. I edited. I did mean Mohm*

Okay, I'll review my soldering. I'm gonna try and pick up some better flux. I'm using a no-clean that's just the consistency of IPA, so it burns off VERY fast. I suppose I'll get a more "swimming" action out of paste flux.

[reformatt]

When doing QFN's like this IC, the centre pad aligns the chip into place. Remove the heat, then apply you tweezers on top, and reapply the heat to push the chip flush onto the board. Then trim up the sides with flux and an small iron tip to remove the excess. If you don't push it down, you won't make good contact on the board.

Echo MON2 on REGEN. Without it, nothing will work on the BQ chip. The REGEN output is a 6V linear regulator derived from the Vcc input when ACDET is above 0.6V. If it's missing, it's either the chip isn't making good contact (and not receiving ACDET or VCC), the chip itself is faulty, or the REGEN line is low resistance. This linear regulator will only supply 100ma max.