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?