(Acer Nitro 5) Shunt resistor– how to read boardview (and schematic) ?

[corrize]

Acer Nitro AN515-52 Compal LA-F951P r1A

Hello, I found a bad cap and removed it, the 19v rail is now not shorted to ground anymore. This short killed the first mosfet each time I replaced it. And not anymore. So I was thinking the laptop was fixed. But no. I pluged the charger and the first 2 mosfet seems ok, but blocked. And shunt resistor is shorted at its two pins (not to ground).

I supect now a bad solder on one component (my fault) or another component dead following first badcap ? I dont know.

For diagnose, I'm blocked on the boardview, I dont understand why shunt resistor have 4 differents pins ? This resistor on board has only two pins obviously, but the boardview show 4 pins not linked 2 by 2. It show 4 pins. The schematic show two pins… and two other linked in dotted lines. I dont understand ?


Could you explain pls ?

[mon2]

Re: (Acer Nitro 5) Shunt resistor– how to read boardview (and schematic) ?

The 4 legs are to alert you that this is a shunt / current sense resistor. Replace it if needed with the same number of pads and resistance as the original. It is required to properly gauge the current through this power rail. The resistance should be the same as the original.

https://components101.com/articles/w...-and-selection

[corrize]

Re: (Acer Nitro 5) Shunt resistor– how to read boardview (and schematic) ?

Ok, thanks, I guess I understood the principle of shunt (for measuring current), that's why I expected to find continuity on the boardview, between pins 3 - 4 and between 1-2. But on the boardview the four go in four directions, without any link between us. Dotted lines on a schematic ok, but on a boardview… made for testing continuity, it's very troubling. True or false ? (I suspected something hided in multilayer).

So, I consider on the boardview : 1-2 same pad and 3-4 same pad too.

I guess this shunt resistor is OK because it's should be strong. But maybe I'm wrong ? Have you already saw shunt resistor dead ? I guess a mosfet will blow up before ?

[mon2]

Re: (Acer Nitro 5) Shunt resistor– how to read boardview (and schematic) ?

Rare for such resistors to be damaged. For now, do not worry about this part. Still required to be on the logic board so the local switching regulator can monitor the current being consumed by this voltage rail via the voltage drop across the shunt resistor.

[corrize]

Re: (Acer Nitro 5) Shunt resistor– how to read boardview (and schematic) ?

I have now a doubt between the first mosfet after power jack, and charging chip.

I measured at this mosfet ;
source : 19v
gate : 4,8v
drain : 3,1v

At first, I concluded this mosfet has leak, and it’s dead, because I guess this mosfet has two states : open or closed. And closed state =0v.

But, maybe it’s the charging chip wich trigger the mosfet by providing two states. For example : 0v (closed) or 19v (open). And if this chip has leak, the mosfet is triggered proprotionaly the voltage. That could explain the low voltage at the gate. In this case, it’s the charging chip wich could be faulty.

How that’s works please ? Wich case is good one ?

[ktmmotocross]

Re: (Acer Nitro 5) Shunt resistor– how to read boardview (and schematic) ?

check what is your chip and read datasheet

[corrize]

Re: (Acer Nitro 5) Shunt resistor– how to read boardview (and schematic) ?

I tryed. On the ship : AwV8JK (or AWVBJK ?) and schematic : ISL88739AHRZ-T and no datasheet except light datasheet, empty.

[corrize]

Re: (Acer Nitro 5) Shunt resistor– how to read boardview (and schematic) ?

Update : I dont found any direct fault to mosfets and charging IC.
I checked (ACIN) of charging IC ; the check if the drain voltage of first mosfet is not too high. And charging IC receive the OK flag.

After, on the line from IC charging wich provide 19v to the source of first mosfet, I found 0.7v. On this line, I found a resistor wich seems in open line state. Unable to measure any resistance on any multimeter range. So, faulty I guess. It is usual issue for resistors to be open line pls ?

[corrize]

Re: (Acer Nitro 5) Shunt resistor– how to read boardview (and schematic) ?

Update : laptop fixed. I replaced bad resistor measured 9Mhoms finaly, instead of 4Khoms. This resistor is on the line : CMSRC_CHG, wich go from the source of two first mosfet to charging IC. I dont found what's it do in the circuit ?
At the end, I replaced 1 damaged badcap, wich causing issue, and 1 mosfet and 1 resistor. Thanks.

[ktmmotocross]

Re: (Acer Nitro 5) Shunt resistor– how to read boardview (and schematic) ?

CMSRC -ACDRV charge pump source input.

[corrize]

Re: (Acer Nitro 5) Shunt resistor– how to read boardview (and schematic) ?

OK that means it’s 19v from source of mosfets for charging battery ?

Update : I used the laptop a half of day and I opened it for add ssd and ram, and when I pressed button… Nothing. It dead again. I dont looked more, I juste saw the charger locked, so there is a short.

[corrize]

Re: (Acer Nitro 5) Shunt resistor– how to read boardview (and schematic) ?

Update :
MOSFET 1
Drain-source-gate ; all shorted (0 Homs)
(not to ground)
= mosfet dead
MOSFET 2
Drain-ground : short (0 Homs)

Shunt resistor to gnd : 0.5 Homs. So 19v rail is shorted.
What can I deduce of 0.5 Homs, it's not bac cap on 19v rail ? Bad cap should be 0homs not 0.5 ? So rather semi conductor shorted ?

[mon2]

Re: (Acer Nitro 5) Shunt resistor– how to read boardview (and schematic) ?

1) remove mosfet1 (PQ310) - is +19_VIN stable from your adapter ?

2) with PQ310 left off the logic board, check for shorts to ground on all pins of PQ310. Leave PQ310 off.

3) check for shorts to ground on PQ311 (while mosfet is on the logic board). If there are shorts to ground, remove PQ311 and check again for shorts.

Check for shorts to ground on the current sense resistor @ PR303.

4) If there is a short to ground on PR303, remove it and check again for shorts.

[corrize]

Re: (Acer Nitro 5) Shunt resistor– how to read boardview (and schematic) ?

Thanks,
PQ310 removed. Short drain-source-gate gone. So mosfet is dead.
It was not shorted to ground before, now pads are not shorted too.

PQ311 keep shorted to ground because it drain goes to shunt resistor, so « normal » it is shorted. So not needed to remove it (and I try to disolder as less as possible).

Rremoving shunt resistor will indicate if charging IC is dead (has an internal short ) or if PC306 is shorted ?

I dont know if power supply is stable ? Maybe not. When the laptop was fixed, it worked fine long time on battery, with 10 restarts ok. And I plugged the charger, it worked fine too 1 hour, I tryed with game. It’s only when I opened it (it was off), unplugged but internal battery plugged. I added NVME drive and ram, and when I tryed to start (opened), nothing. So yes, maybe power supply, I cant test it. Next time, I will probably try with another and without battery.

[corrize]

Re: (Acer Nitro 5) Shunt resistor– how to read boardview (and schematic) ?

Update ; another damaged cap (PC302) found, removed and the short is gone. I will order a mosfet and i thinks it fixed again. I saw before it was damaged, but so little, I dont replaced it.
When i opened the laptop, maybe I touched it or when I used it for gaming, it finished to die ? I dont thinks the charger or battery are faulty. I'll be carefull though.

Acer Nitro 2 - Corrize 2 (end of game I hope)