HP 255 G9 dead

[DrFalken]

Hi guys,
yesterday a client brought this laptop completely dead.
I've found liquid spill on the motherboard's top.
Battery removed.
ACDRV_CHG_R missing on both PQB11 & PQB12.
BQ24735 readings:
- VCC: 19V
- ACDET: 2.91V
- REGN: 6V
- ACOK: 0
- SRP/SRN to GND: 1V floating
- PRB11: 0
What sould I check ?
Can I swap BQ24735 with BQ24738 ?
Thank you !

[mon2]

ACDRV_CHG_R missing on both PQB11 & PQB12.

1) charger sticky article by piernov above

2) Confirm the main power rail is not shorted to ground through a resistance check.

3) Review PQB11 & PQB12. Remove all power. Meter in resistance mode.

Measure the resistance of:

source / drain
source / gate
gate / drain

Post each measurement. Test each DCin mosfet.

[DrFalken]

1) charger sticky article by piernov above

2) Confirm the main power rail is not shorted to ground through a resistance check.

Confirmed, not shorted.

3) Review PQB11 & PQB12. Remove all power. Meter in resistance mode.

Measure the resistance of:

source / drain
source / gate
gate / drain

Post each measurement. Test each DCin mosfet.

PQB11:
- source / drain = 3 MOhm
- source / gate = open
- gate / drain = 3.36 MOhm

PQB12:
- source / drain = 3.1 MOhm
- source / gate = open
- gate / drain = 3.7 MOhm

PQB13:
- source / drain = 1.4 MOhm
- source / gate = open
- gate / drain = 3 MOhm

[mon2]

Can you link the schematic for this board?

[DrFalken]

Can you link the schematic for this board?

Sure

link to schematic - https://www.badcaps.net/forum/troubl...ardview-please

[mon2]

Remove all power. Meter in resistance mode. Measure the resistance to ground of ACIN.

Measure the voltage to ground of ADP_ID - this analog voltage is sampled by the EC to gauge if the power adapter is suitable to power the logic board.

[DrFalken]

Remove all power. Meter in resistance mode. Measure the resistance to ground of ACIN.

Measure the voltage to ground of ADP_ID - this analog voltage is sampled by the EC to gauge if the power adapter is suitable to power the logic board.

ACIN (@PRB15) = 168.6 kOhm
ADP_ID = 0

[mon2]

Issue is linked to the ADP_ID. A voltage is applied starting at the DCin connector. Confirm it.

Then to a resistor based voltage divider which presents a lower and safe voltage onto the EC. Test each leg of this circuit. Most likely the voltage from the adapter is absent at the power connector but confirm it.

After all this, the EC believes the power adapter is not worthy of powering the board.

[DrFalken]

Issue is linked to the ADP_ID. A voltage is applied starting at the DCin connector. Confirm it.

Then to a resistor based voltage divider which presents a lower and safe voltage onto the EC. Test each leg of this circuit. Most likely the voltage from the adapter is absent at the power connector but confirm it.

After all this, the EC believes the power adapter is not worthy of powering the board.

Checked ADP signal (center pin) directly at power connector of 2 different (one Sandberg and one Chicony brand, both working with other laptop) PSU:
- First PSU is 0.02V
- Second PSU is 0.10V
When I plug the connector, ADP_SIGNAL (pin 6 @PJP1) is 0.
ADP_SIGNAL to GND = 19.9 kOhm

[mon2]

Are the working laptops from HP? With HP branded power supplies? This is important. While Dell uses a digital 1-wire communication with the center needle pin; HP uses an analog voltage.

[DrFalken]

Are the working laptops from HP? With HP branded power supplies? This is important. While Dell uses a digital 1-wire communication with the center needle pin; HP uses an analog voltage.

Yes, HP 255 G7

[mon2]

ADP_SIGNAL to GND = 19.9 kOhm

What is the ADP_SIGNAL to ground on the non-working board? (No power to the board during resistance checks)

[DrFalken]

What is the ADP_SIGNAL to ground on the non-working board? (No power to the board during resistance checks)

With and without PSU plugged:
ADP_SIGNAL to GND = 19.9 kOhm

(PSU always disconnected from power)

[mon2]

Measure the resistance between pins # 1 & 2 directly on the charger IC.

[DrFalken]

Measure the resistance between pins # 1 & 2 directly on the charger IC.

You mean BQ24735 ?
Pin 1-2 = 0 (or very low...maybe because of PRB1)

[mon2]

This is ok.

Is PQB2 onboard? If yes, flux and remove it for testing.

[DrFalken]

This is ok.

Is PQB2 onboard? If yes, flux and remove it for testing.

No, nothing of "protection for reverse input" is onboard...

[DrFalken]

Replaced BQ24735 with BQ24738, now I read 1.28V @ACDRV_CHG_R
Update: replaced PQB11 but ACDRV_CHG_R drop again to 0

[mon2]

Carefully flux and remove the series ~4K ohm resistor on the acdrv pin. Power up and test if acdrv is boosted to about 25v or not.

[DrFalken]

Carefully flux and remove the series ~4K ohm resistor on the acdrv pin. Power up and test if acdrv is boosted to about 25v or not.

Resistor removed (PRB9).
ACDRV_CHG = 0.9V
Replaced also PQB12 & PQB13 with AON7752: same reading.