Acer - N19C2 - MB EH7LW - Sudden death

[samstown]

Re: Acer - N19C2 - MB EH7LW - Sudden death

Bad luck.. this morning PC doesn't start anymore, no sign of life. I'll have to reopen it.

[samstown]

Re: Acer - N19C2 - MB EH7LW - Sudden death

Looks like UQ2 explode...

[mon2]

Re: Acer - N19C2 - MB EH7LW - Sudden death

Crap. See attached for UQ2 datasheet. This is a load switch (solid state relay).

Remove the defective part and check the resistance to ground for the output rails @ pins 8 & 9 of this component.

Order a few of these for replacement and future use.

[samstown]

Re: Acer - N19C2 - MB EH7LW - Sudden death

Thank you, I'll check.

[samstown]

Re: Acer - N19C2 - MB EH7LW - Sudden death

This is UQ2... I see the little crack, so that's what I tought it's the source of problem now. What do you think ? I've put the pin in red, that's correct ?

I have 0V on Pin 1 and 2 and 0.25 on 8 and 9

[mon2]

Re: Acer - N19C2 - MB EH7LW - Sudden death

Please see page #14 of the data sheet. Where you see the chipped area is pin #1.

That is, the ic is soldered upside down so from the shared pic, pin #1 is the very bottom right of the part.

This is the input voltage to the load switch.

Then top left are pins 8&9 = output of the load switch.

Remove all power and check the resistance to ground of pin #1.

Then check the resistance of pin #8.

Post the readings.

The issue maybe upstream since the input voltage is not correct.

Where is the voltage for this load switch created?

Also check and post the voltage on pin #3 of this part. This is the enable for the load switch.

[samstown]

Re: Acer - N19C2 - MB EH7LW - Sudden death

Hello,

my apologize. I got sick and forgot to reply. I'll double check this week.

Thanks

[Coguar]

Hello, I have a similar situation, with the difference that on my laptop, due to a fault in the charger connector, there was a 19V voltage present on the ACDET. When I removed the connector and applied 19V to the power pin and shorted the GND to ACDET, the laptop does not turn on. While there is a battery, it turns on and works, but it doesn’t charge and doesn’t work only on the charger without the battery. Please, any advice on where to start? Thank you.

[mon2]

ACDET at 19v is too high and may have killed the charger IC. This signal line should be ~2v4 or so after being conditioned by a resistor based voltage divider.

What is the voltage on ACDET now with the power adapter?

[Coguar]

something around 2.57v , PQB3 mosfet on one side have 19V (source) @ drain 0.07v, at Gate something like 0,059v

[mon2]

Ok. ACDET is now ok but the gate (ACDRV) voltage to the DCin mosfets is not. There may be a reason for this. First check if the main power rail that follows these 2 x DCin mosfets is shorted or not.

With no power to the board (no battery either), measure the resistance to ground on pins 5-6-7-8 (any one will be ok) of PQB4. If the resistance is low, then there is a short on the main power rail and the charger IC is shutting down the DCin power path on purpose.

If the resistance is ok and high, then at least one of the 2 x DCin mosfets is defective.

To test, with no power to the board, test the resistance across each of these DCin mosfets:

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. Repeat for each mosfet @ PQB3 and also PQB4. Each measurement must be hundreds of k ohms or higher. If not as high, then the part is likely to be defective.

[Integra]

PQB3
source to drain 355k ohms
source to gate 295k ohms
gate to drain 8.66k ohms

PQB4
source to drain 8k ohms
source to gate 0.10 ohms, checked again and now it is show 8k ohms
gate to drain 28k ohms

so PQB4 is defective ? but i think that i tested it off board and was fine I think.
cant remember
ps Coguar is my workmate, he starded job, and ask me to answer here and continue becouse he has to leave now.

[mon2]

What is the resistance to ground on PQB4 - drain pins 5-6-7-8 ? This is important to know if the main power rail is shorted or not.

PQB3
source to drain 355k ohms
source to gate 295k ohms
gate to drain 8.66k ohms

PQB4
source to drain 8k ohms
source to gate 0.10 ohms, checked again and now it is show 8k ohms
gate to drain 28k ohms

Both mosfets are suspects as each is with a low resistance. Suggest to flux and remove both of these mosfets and test each again after they have cooled down and on your workbench.

[Integra]

removed from board values:

PQB3
source to drain 8k ohms
source to gate 0L
gate to drain 0L

PQB4
source to drain 8k ohms
source to gate 8k ohms
gate to drain 0L

it is really hard to measure this small components and getting diffrent values all times.
But DCA 75pro detects on both parts n chanell mosffet if that mean someting.

i have few multimeters and every one gives diffrent values.

update: replaced both mosfets and still there is no voltage on drain for PQB3
what voltage to except on gate ?
and if my gate voltage 0.290v is to low, whete to find problem? tnx

[mon2]

The charger IC is the TI BQ series and this series drives N-channel mosfets which are onboard your logic board. The ACDRV voltage should be = adapter voltage + REGN voltage = 19v + 6v = ~25v to enable the N-channel mosfets in the power path.

Now that the DCin mosfets have been replaced, measure the voltage to ground of the REGN pin # 24 on the charger IC @ PUB1. This must be a stable ~6v to ground. If not, check the VCC pin # 28 on PUB1 which must be close to the adapter voltage. If it is not, then the dual diodes or series resistor present on pin #28 are suspects. This is a common fault. If the charger IC is not powered through the VCC pin, the ACDRV voltage will not be available nor at the REGN pin.

You have also not reported the resistance to ground on the drain pins of the mosfet @ PQB4. This is important to know.

[Integra]

I have a new update if this information is useful to you: I made one modification. I added 19V to the ACDRV_CHGR pin, and now the MOSFETs are enabled. I also have voltage on the drain for both MOSFETs. The laptop turns on, but it's still not charging.

I noticed with a thermal camera that the BQ chip is hot (around 47°C) even with no battery connected. After I get a picture, a message appears: "BATTERY CRITICAL LOW," and the laptop turns off, even though the battery is not connected. I get same message when laptop work on battery without charger,but battery is realy drained 10,2v.

Maybe the replaced MOSFETs are the cause, as they are not the same as the original ones, but they seem to be working.

Now drain of pqb3 have 17v, gate is 19v, PQB4 drain is on 16.90v, gate 19v.

I will measure what you suggested tomorrow. I have to leave now. Really thanks for your help. This site is great, and I will support it for sure.

So, is my BQ 24800 TI128AL9N chip dead? And where can I find a replacement?

Thanks!

[Integra]

hi still didnt fix this laptop, cant find excat BQ chip, any idea about where to find compatible one ?

[Integra]

The charger IC is the TI BQ series and this series drives N-channel mosfets which are onboard your logic board. The ACDRV voltage should be = adapter voltage + REGN voltage = 19v + 6v = ~25v to enable the N-channel mosfets in the power path.

Now that the DCin mosfets have been replaced, measure the voltage to ground of the REGN pin # 24 on the charger IC @ PUB1. This must be a stable ~6v to ground. If not, check the VCC pin # 28 on PUB1 which must be close to the adapter voltage. If it is not, then the dual diodes or series resistor present on pin #28 are suspects. This is a common fault. If the charger IC is not powered through the VCC pin, the ACDRV voltage will not be available nor at the REGN pin.

You have also not reported the resistance to ground on the drain pins of the mosfet @ PQB4. This is important to know.

resistance to ground on pqb4 is 3.37 Kohm

on PIN 28 i have a 18.18V, but on pin 24 i dont have 6v, just 0.027v
and reason is that i have short to ground on thath pin, around 19 ohms
so again remove BQ and than measure ?

[mon2]

No short here.

BQ24800 charger IC:

https://www.digikey.com/en/products/detail/texas-instruments/BQ24800RUYR/12165702

https://www.aliexpress.com/w/wholesale-BQ24800.html?spm=a2g0o.home.search.0

Order a few spares. Even a few of the linked mosfets is a good idea as they are low cost.

[Integra]

Thanks, I found the BQ chip and replaced it, now I get the voltage on the battery connector, though it is very low, about 10V. After charging the battery manually, the laptop is turning on, and the critical low battery error is not showing up anymore. The issue that still persists is that the laptop does not work without the battery, it turns on, but shows the same critical low battery error, and shuts down. When the battery is connected and the laptop is working, the battery wont charge.

Also one thing to note is that even after changing the BQ chip, the pin #24 does not show 6V.