Acer laptop with LS-E892P motherboard - 10 mA

[Askic]

Hello,

I have a laptop Acer with motherboard LS-E892P. The first input MOSFET was OFF (PQ302) and the next PQ303 was also off and voltage was not present after it. So in order to troubleshoot, I baypassed this first MOSFET and after that 19V was present on the motherboard (through FW diode on second MOSFET). Motherboard doesn't start and the current is about 10 mA. There is no short circuit. On LB1 is present and stable +3VLP_EC (3.29V), this voltage is present on superIO chip. On SPI ROM chip (BIOS), on pin 8 +3VALW_SPI is not present, there is 0 V.
Attached is the schematics for LA-E891P, but it is very similar. I wonder what to inspect next.

Schematic -> https://www.badcaps.net/forum/showthread.php?t=123071

Thank you.

[Techtiger]

Re: Acer laptop with LS-E892P motherboard - 10 mA

Voltage on PQ303 all pins & BQ24735 all pin & RT6575 all pin ?

[mcplslg123]

Re: Acer laptop with LS-E892P motherboard - 10 mA

+3VALW & +5VALW will be generated after power on. So you are not supposed to get any voltage at pin8 of bios chip. Go by @techtiger's suggestion and fix the input keys not opening first.

[Askic]

Re: Acer laptop with LS-E892P motherboard - 10 mA

@mcplslg123, thank you for the clarification. I thought that ALW means ALWays.

I have measured voltages on all pins.
PU301 (BQ24735):
1->18.2V 2->18.2V 3->18.6V 4->18.4V 5->0V
6->2.3V 7->0V 8->3.3V 9->3.3V 10->0.78V
11->3.1V 12->3.1V 13->3.1V 14->0V 15 ->0V
16->6V 17->5.8V 18->3.1V 19->3.1V 20->17.8V

PU401 (RT6575):
1,2->0V 3->3.2V 4,5,6,7->0V 9->4.5V 10->0V
11->0V 12 ->17.8V 13->1.3V 14,15,16 ->0V
17->1.1V 18.19->0V 20->3.3V

On PQ303 all pins have 18V

[Techtiger]

Re: Acer laptop with LS-E892P motherboard - 10 mA

@mcplslg123, thank you for the clarification. I thought that ALW means ALWays.

I have measured voltages on all pins.
PU301 (BQ24735):
1->18.2V 2->18.2V 3->18.6V 4->18.4V 5->0V
6->2.3V 7->0V 8->3.3V 9->3.3V 10->0.78V
11->3.1V 12->3.1V 13->3.1V 14->0V 15 ->0V
16->6V 17->5.8V 18->3.1V 19->3.1V 20->17.8V

PU401 (RT6575):
1,2->0V 3->3.2V 4,5,6,7->0V 9->4.5V 10->0V
11->0V 12 ->17.8V 13->1.3V 14,15,16 ->0V
17->1.1V 18.19->0V 20->3.3V

On PQ303 all pins have 18V

ACIN is not recognize by KBC, your ACDRV is low +18V since you have jump the first fet 2nd FW there is a drop voltage you have to solved (BQ24735) fist to move forwed on ACDRV line you have 2 components check if they are faulty

for RT pin 13 must be LDO +5V in you case 1.3V EN 1 is 3.3V but EN2 0V pin 12 voltage is low

[mcplslg123]

Re: Acer laptop with LS-E892P motherboard - 10 mA

ALW-Yes it does mean Always but on newer platform there is concept of suspend logic and "Deep Sleep Well". Thats why you will notice consumtion of say eg 0.015ma at the beginning and after a while it will drop to say 0.004. Thats 'coz deep sleep well is activated. In this scenario laptop remains on DSW state and not S5 stage by default. When you press power button, it will get back to S5 state and then only 3/5V ALW will be generated. This is done to save power. However, 3/5V does get generated on most boards at the beginning (when consumption is say 0.015ma) for a very brief interval and then it will go to DSW stage.