Acer Aspire A515-56 Main FH5AT LA-K093P no power

[Egidio85]

Hi everyone, I was looking for some advice on an Acer Aspire A515-56 with a FH5AT LA-K093P motherboard.

the PC does not turn on, the battery is completely dead.

checking the board I do not detect shorts.

the 19v of the charger stops at the first mosfet PQB3

on PUB1 BQ24781 pin 28 I have 19v.

connecting with a bench power supply I have no absorption.

nothing that heats up with a thermal camera.

any advice on what to check?

thanks in advance

[mon2]

Hi. Yes, review the detailed sticky article above by piernov on charger circuits.

Remove all power. Meter in resistance mode.

Measure the resistance across the first DCin mosfet:

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. Each measurement must be hundreds of k ohms or higher else could be shorted. Repeat for the 2nd DCin mosfet.

Also check the resistance to GROUND of the 2nd DCin mosfet - test the source (1-2-3) pins and also the drain pins (5-6-7-8). We are checking this to confirm the final output of these DCin mosfets is not shorted for the main power rail which may be the reason for the damage of the DCin mosfets.

Being N-channel mosfets, the gate pin of both DCin mosfets should be = adapter_voltage + REGN voltage = ~25v to fully enable.

[Egidio85]

thanks for the reply, here is the measurement

first mosfet PQB3

source (1-2-3) & drain (5-6-7-8). 67K ohm
source (1-2-3) & gate (4). 85K ohm
gate (4) & drain (5-6-7-8) 1.2M ohm

second mosfet PQB4

source (1-2-3) & drain (5-6-7-8). 800K ohm
source (1-2-3) & gate (4). 600K ohm
gate (4) & drain (5-6-7-8) 800K ohm

second mosfet PQB4

gnd source (1-2-3) 110K ohm
gnd drain (5-6-7-8). 6K ohm

[mon2]

Flux and replace the first Dcin mosfet at PQB3.

[mcplslg123]

DC jack often fails on this board blocking 19V.Check it to be sure.

[Egidio85]

Flux and replace the first Dcin mosfet at PQB3.

changed the first mosfet. same situation, behavior does not change

[mon2]

Which mosfet was used for the replacement? With no power, share the same resistance checks for this new mosfet.

Then, attach the power adapter and carefully measure the voltage to ground for the following pins:

Using BQ24780S as reference which is with the same pinout -

REGN
VCC
ACDRV
ACOK

Also ACDET.

[mon2]

As per post #5 - confirm the attached which may be the root cause. We have seen this a few times on this forum.

In summary - the ADAPDET pin on the power connector is failing to provide the 0V or GROUND. Respectively, the ACDET voltage is then pulled to ground due to the mosfet @ PQ101.

As a test, you can connect a piece of wire to the gate pin of PQ101 to GROUND which will force PQ101 to DISABLE. Then ACDET should follow a voltage suitable to enable the mosfets.

[Egidio85]

As per post #5 - confirm the attached which may be the root cause. We have seen this a few times on this forum.

In summary - the ADAPDET pin on the power connector is failing to provide the 0V or GROUND. Respectively, the ACDET voltage is then pulled to ground due to the mosfet @ PQ101.

As a test, you can connect a piece of wire to the gate pin of PQ101 to GROUND which will force PQ101 to DISABLE. Then ACDET should follow a voltage suitable to enable the mosfets.

Thanks for the advice, by putting pin number 2 of the PQ101 to ground the PC started working again. Can I leave it like this? Or could it cause problems?

[mon2]

You can leave this wire jumper and use the laptop like normal. The root cause is as noted by mcplslg123, the dcin power adapter connecter is likely loose for this pin that should have pulled this mosfet gate pin to ground.

The manual wire jumper now performs the same task.

[Egidio85]

ok, thank you so much for your help

[mcplslg123]

Wiser to replace the DC jack as it already shows signs of failure. Why risk it?

[alex26]

Hello. I had the same problem with the DC jack, but the laptop still did not work. Now it turns on, but it shows Critically low battery and then turns off. The battery is completely discharged. There is also a BIOS reset button, but even though I tried, I still can't get rid of that message. The battery measured in the BIOS shows 3V. Where could the problem be? Thanks.

[mon2]

alex26 - same motherboard? LA-K093P

The board will not power on with the OEM power adapter? I recall similar other posts on this forum with this fault.

Locate mosfet PQ101 (3 pin device). Measure the voltage to ground of ACDET with the power adapter connected. Suspecting it will be 0 volts.

Then measure the voltage to ground of pin #2 = gate pin on PQ101. Suspecting this will NOT be 0v. Share the feedback.

Summary: The dcin power connector, when it is working properly, will pull DOWN the voltage on pin #2 of PQ101. This low voltage on gate pin will turn PQ101 OFF. When PQ101 is OFF, the ACDET will be a positive (ie. not zero volts) to the battery charger.

Believe at this time that the gate pin is floating from the DCin power connector so the PQ101 is ENABLED using the voltage divider resistors on the gate pin. This pulls ACDET to zero volts so the battery charger IC believes no power adapter is attached and fails to charge the battery.

Assuming this all to be accurate - flux and remove PQ101 mosfet. This should allow for ACDET to be a positive and valid voltage to enable the battery charging (provided the battery is not too old and dry).

[alex26]

It s the same motherboard. I did this, I have 2.9v on the ACDET pin. Now the laptop starts completely, I have all the voltages but it shows Critical low battery on the display,and than off. If I inject voltage into the battery it doesn't charge

[mon2]

Remove the battery and test if the board powers up using the adapter only. It should.

The battery may be too deeply discharged and causing this shutdown event. Perhaps locked since you mentioned it does not charge with an injection on the battery. Test with another known good battery (Amazon?).

If the unit powers down using only the adapter then something else may be wrong. Will need the voltage to ground measurements on the battery charger IC to move further.

[alex26]

With the battery disconnected and only the charger plugged in the laptop it show Critical low battery. I measured the voltage on Bq chip and look good, i even change it.

[mon2]

With only the power adapter, the unit stays ON?

Measure the voltage to ground on each pin on the battery connector (without the battery connected). We are most interested in the SMBUS line voltages (SCL / SDA).

[alex26]

Only with power adapter the unit stay on, and after few seconds the laptop displayed Critical low battery and then off. I can't measure the voltages right now because I'm not at home, but I'll be there in 2 hours and I'll post.Thank you very much for wanting to help me.

[alex26]

Now the laptop doesn't want to start at all. The current drawn by the board is 10-20mA but sometimes 130mA. I noticed a strange problem with the PUZ1 integrated circuit. It has voltages on pins 10 and 29 = 5V, on pin 22 = 19V, but on pins 23 I have 0.1V but also 5.9V, on pin 24 I have 0V but also 1.7V or 4V, and on pin 12 I have 0v or 0.6V. These voltages change if I put a drop of isopropyl alcohol on the PUZ1 integrated circuit (RT3612). Before ordering the RT3612 I said I would try to program the EC chip and I would need a bin. I am also attaching the original bin. The serial number is no longer visible on the laptop label. It is an Acer Aspire 3 model N20C6, motherboard FH5AT LA-K093P rev.1.C