Missing VCCSA lenovo ideapad 300-15isk

[sparrow2719]

Hi, motherboard code:
BMWQ1 BMWQ2 NM-A481
Rev 1.0

When plugged in the charger, the power light instantly ON, no fan spinning, battery RTC connected and good.

The on off button not responsive at all, must be pressed about 10 seconds or more and then the power light just blink a little, the fan just move a little bit and stop...and nothing. Measurred ONOFF# pin=3.3v on power button board and it goes to 0v when pressed.

No vcc core at all
No vccsa
nvidia core is ok
1.8v alw is ok
1v alw is ok
1.35v ddr is ok

I have replaced the processor voltage regulator buck NCP81206, now vcc core is available ok but still no vccsa present.

Help anybody ?

[on/off]

Re: Missing VCCSA lenovo ideapad 300-15isk

Did you have DRON signal?

[sparrow2719]

Re: Missing VCCSA lenovo ideapad 300-15isk

Did you have DRON signal?

DRON = 5V
PWM = 2V
No output.

Mosfet checked out and replaced also.

[on/off]

Re: Missing VCCSA lenovo ideapad 300-15isk

DRON = 5V
PWM = 2V
No output.

Mosfet checked out and replaced also.

Seem it's correct. Maybe NCP81253 need to replace.