Lenovo Ideapad 3 15IIL05 NM-D031 +3VALW missing

[FrozenHaxor]

Hello,

Having an issue troubleshooting this board, it takes no current. PQ100 MOSFET gets 0V on the gate and does not open, when I short it out the laptop powers up. There is 0V on ACDRV from BQ24780, 0V on ACOK.

Now for the fun part, ACOK is pulled up to 3VALW rail, when I short out the PQ100 and power up the laptop, ACOK jumps up to correct 3.3V, as soon as I remove the short across the MOSFET it goes fully dead again. Now my issue is that according to schematic this is a circular logic, I can't have +3VALW without getting power to the PU1101 SY8386BRHC, but I can't get power to that chip unless PQ100 opens and powers up the main PR100 resistor. The internal LDO of BQ chip works and outputs 6V so it gets the power. ACDET is at 2.72V

What am I missing?

Schematic and BoardView: https://www.badcaps.net/forum/troubl...59#post1654359

[lapfix]

Many others measurements to take.
PQ101 is it OK (Diode mode)
PR100 measure with resistance mode
PU100 voltages : PIn 3 /4 /5

[FrozenHaxor]

Many others measurements to take.
PQ101 is it OK (Diode mode)
PR100 measure with resistance mode
PU100 voltages : PIn 3 /4 /5

PQ101 is okay
PR100 is good (0.03Ohm)
PU100 pin 3 0V
PU100 pin 4 0V
PU100 pin 5 0V

[lapfix]

PR100 resistance to GND to know if there's a short at 19v rail
you can also check all colis for short

what do you mean by : when I short it out the laptop powers up....is there a display !

[FrozenHaxor]

PR100 resistance to GND to know if there's a short at 19v rail
you can also check all colis for short

what do you mean by : when I short it out the laptop powers up....is there a display !

There is no short. When I bypass PQ100 MOSFET (connect drain and source together) I get the laptop to fully power up.

[lapfix]

If there's no short at your motherboard , all coils are not shorted so i suggest to concentrate more at BQ24780S.
This forum is full of informations about it.
from my opinion , if i had 19v at pin 28 / 2.7v at pin 6 / 6v at pin 24 ...so i must find my 6v at pin 5 ( ACOK is pulled up to 3VL rail and not 3VALW rail in general )...and there's no short to gnd at BQ pins....so i change it simply .
ACOK must be 6V in this case get it from BQ24780_VDD

Is PR112 /PR111 populated at this motherboard !!

[FrozenHaxor]

If there's no short at your motherboard , all coils are not shorted so i suggest to concentrate more at BQ24780S.
This forum is full of informations about it.
from my opinion , if i had 19v at pin 28 / 2.7v at pin 6 / 6v at pin 24 ...so i must find my 6v at pin 5 ( ACOK is pulled up to 3VL rail and not 3VALW rail in general )...and there's no short to gnd at BQ pins....so i change it simply .
ACOK must be 6V in this case get it from BQ24780_VDD

Is PR112 /PR111 populated at this motherboard !!

ACOK can't be 6V, it's pulled up to the +3VL rail only. It goes to 3.3V when I bypass the MOSFET and boot the board.

There is no PR112 or PR111 populated.

[FrozenHaxor]

Case closed, replaced faulty BQ chip, it was not driving the PQ100's gate at all. Replaced PQ100 preemptively as well if it turned out to be the cause of BQ's failure. Power rail sequence is now correct. Thanks for the support.

[lapfix]

Case closed, replaced faulty BQ chip, it was not driving the PQ100's gate at all. Replaced PQ100 preemptively as well if it turned out to be the cause of BQ's failure. Power rail sequence is now correct. Thanks for the support.

Good news
Can you please share the BQ voltage

[FrozenHaxor]

Good news
Can you please share the BQ voltage

I put the laptop together already, but the gate drive voltage from ACDRV was a nice 24.7V as it should be, ACOK at correct steady 3.3V, ACDET at 2.7V.