Acer Aspire 5 (A515) No power

[pabloroggeri]

I friends.

I have a problem that I can't solve. The 19V input voltage does not go beyond the first FET PQB3. If I make a jumper from the input of the charger to the output of the second FET (disconnecting the battery) the laptop turns on. That is to say, the BQ24800 charger IC does not activate the input FETs, when measuring the gates there is 0V. I put the charger IC in another laptop to test and it works, that is, the fault is not in the BQ24800.

I made these measurements on the BQ24800:

VCC on pin 28 ok, it has 18.5V.

Pin 6, ACDET 2.6v, ok

Pin 11 and 12 EC_SMB, 0V (that is normal since there is no 3.3V)

Pin 24: +6V_CHG_REGN : 6V, OK


Pin 15 BATPRESS (it is a protection, normally it has 0V): 0V

The input and battery charging FETs are not shorted, nor do the capacitors mark me as short. The resistances of the resistive divider for ACDET are at their values according to the schematic diagram (PRB11 and PRB13)

I'm going crazy, has anyone had this error?




Motherboard: Mother LA-K091 REV 2.0

[mon2]

Hi.

1) Recommended reading - soon to be promoted by Oprah when her laptop dies:

Laptop battery charging circuit - Badcaps

2) What is the voltage to ground of pin # 4 (ACDRV) on the BQ24800 ? With the power adapter connected, ACDRV should be ~25 volts to enable the DCin mosfets.

3) Carefully measure the voltage to ground of each pin of each of the DCin mosfets.

Interested in the following measurements:

source (1-2-3)
gate (4)
drain (5-6-7-8)

Repeat to measure for the 2nd DCin mosfet.

4) Also, share the voltage to ground of ACOK (pin # 5) on BQ24800.

[pabloroggeri]

Thanks for answering:

I had forgotten to mention these measurements:

2) Pin 4 ACDRV: 0V

3) 19V at drain PQB3, 0V at source PQB3, 0V at drain PQB4, 0V at source PQB4

0V in both gates of PQB3 and PQB4

4) PIN 5 ACOK: 3.23

From what I understand the BQ24800 is not driving the input FETs. I can't understand why.
I have read some of the tutorial, I made the measurements as far as I can understand.

I hope you understand my horrible English, I use Google Translate

[mon2]

Your english is fine

Carefully flux and remove the 4k resistor that should be between the DCin mosfets and the ACDRV pin # 4 on this charger IC. Do not lose this 4k resistor. Then power up again and carefully check the voltage to ground on pin # 4 (ACDRV) of the same charger IC.

Do you see ~25 volts now (without the 4k resistor) ?

ACDRV voltage = adapter voltage + REGN LDO voltage = 19v + 6v = 25v.

Update - remove PQB1 (2N7002 = SOT323 package) off the board and test again. This mosfet may be shorted.

[pabloroggeri]

Your english is fine

Carefully flux and remove the 4k resistor that should be between the DCin mosfets and the ACDRV pin # 4 on this charger IC. Do not lose this 4k resistor. Then power up again and carefully check the voltage to ground on pin # 4 (ACDRV) of the same charger IC.

Do you see ~25 volts now (without the 4k resistor) ?

ACDRV voltage = adapter voltage + REGN LDO voltage = 19v + 6v = 25v.

Update - remove PQB1 (2N7002 = SOT323 package) off the board and test again. This mosfet may be shorted.

The voltage value without the 4K resistor on ACDRV (PIN 4) is 0V

I removed PQB1 (2n7002) and the input FETs still do not activate. I also measured it and it's ok

If I measure with the oscilloscope at the gates of the input FETs, a peak of approximately 15V appears, and it goes away very quickly in a matter of milliseconds.

[mon2]

Remove all power.

Meter in DIODE mode. Confirm that the dual common cathode diode @ PDB1 is not defective.

Red meter probe @ PDB1, pin 3; black meter probe @ pin 2. Should conduct. Reverse the meter leads and there should be no conduction.
Repeat for pins 1 & 2 testing of the same dual diode.

Remove all power.

Meter in resistance mode. Measure the resistance of 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)

Measure for each of these mosfets @ PQB3 and PQB4. Post each measurement.

ACOK is high so the charger IC likes your adapter.

What is the voltage to ground of CMSRC_CHGR ? (add the removed 4k resistor back after the mosfet testing and then apply the power adapter again)

[pabloroggeri]

Remove all power.

Meter in DIODE mode. Confirm that the dual common cathode diode @ PDB1 is not defective.

Red meter probe @ PDB1, pin 3; black meter probe @ pin 2. Should conduct. Reverse the meter leads and there should be no conduction.
Repeat for pins 1 & 2 testing of the same dual diode.

Remove all power.

Meter in resistance mode. Measure the resistance of 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)

Measure for each of these mosfets @ PQB3 and PQB4. Post each measurement.

ACOK is high so the charger IC likes your adapter.

What is the voltage to ground of CMSRC_CHGR ? (add the removed 4k resistor back after the mosfet testing and then apply the power adapter again)

Diode PDB1 is good.
The input FETs are good. I even changed them in case they are open although I think that is unlikely

I am translating the text, I don't quite understand what you are saying about ACOK. The voltage comes from the 6V resistive divider as I understand it.

CMSRC_CHGR has 0V, with and without 4K resistor


I had already done the vast majority of the measurements and checks and I have a lot of experience repairing laptops in the charger section, it has never happened to me that having all these values correctly does not work, especially if I checked the charger IC on another laptop and it works.

[mon2]

ACOK is an open drain output. It will be low if ACDET pin is out of range. Since it is high, the adapter is good.

what is the voltage on CMSRC?

[mon2]

Also review this post :

https://e2e.ti.com/support/power-man...114776#4114776