Lenovo Ideapad 330-14IKB - No Power

[Sofian75]

Main power rail is present but 3.3v alw isn't there and I don't have any voltage at the coil on the 5v rail either.

Trying to focus on the 5v rail first, I don't understand why I have the 5v at the resistance and the input of the capacitor but not at the output (in red).

I ve already changed the capacitor but same thing.
What am I missing?

Thanks

[DeXXter]

I quickly checked the datasheet and those 5v you have there are the VCC line, that's for internal stuff of the chip itself, so don't focus on that. That ic is apparently fine, you don't have voltage on that coil because the laptop is not turning on, check the EC if the pwr_btn is working properly.

[FZG]

The cap side you labeled 0V in red is the ground side. If there is a connection from there to the coil you may have a short somewhere downstream.

[piernov]

This is the bootstrap circuit of the buck converter, the capacitor C6006 does not connect to ground, it does connect to the phase line if the buck converter, before the inductor.
5V is normal on the bootstrap pin as there's an internal diode between the internal 5V LDO and this pin inside the IC.

[Sofian75]

I quickly checked the datasheet and those 5v you have there are the VCC line, that's for internal stuff of the chip itself, so don't focus on that. That ic is apparently fine, you don't have voltage on that coil because the laptop is not turning on, check the EC if the pwr_btn is working properly.

Aren't the 5 and 3.3v rails supposed to be always on?

[DeXXter]

Aren't the 5 and 3.3v rails supposed to be always on?

Sure, but it looks like the laptop is not reaching that state. Apparently u only have 3.3v LDO, so before going to the 5vAlW check if you have those 3.3v on the kbc. Also check the resistance on those coils (specially 3.3v since the kbc gets is power from this) and if you have something when pressing the power button.
Also I would check that EN pin, what do u got there?