Lenovo B50-70 LA-B092P REV 2.0 - short on +3VLP

[kotel studios]

Hi,

My lenovo B50-70 laptop (mainboard compal LA-B092P VER 2.0) had a short on the +3V generation part (where PU401 is).
I've removed the SY8208BQNC and the short is gone on PL402. Although, it's still there on pin 5 "LDO" of the SY8208BQNC (1.8ohms to GND).
All other coils aren't shorted to GND.

Removing the PC412 cap didn't help. Mainboard pads are still shorted. Cap itself is fine.
Pin 20 (+3VLP) of ALC codec isn't shorted too, so it shouldn't be the issue.

Originally, the laptop wouldn't power on. It would get its 20V on the input and that's where I halted diagnosis.
Now, I've checked the main power arena and everything seems to be fine. No shorts to GND.

I have no idea what's the cause of the short on "LDO" pin. Soldering the original SY8208BQNC makes the short re-appear. Only thing shorted on the IC is "LX" and "IN" pads together.
Attaching a schematic for rev 1.0 board (yes, I know it's not rev 2.0 but that's all I could find).

Any ideas?

[Sephir0th]

SY8208B has a special layout, so you're probably simply confusing the pins.

[kotel studios]

So the "LDO" pin is VCC. Well, this is bad. All I know is that it goes to +3VLP (3.3v low power, right?). Where is it generated? Schematic doesn't say it.
Any ideas?

[Sephir0th]

The point here was only to show you the pinout. If you confirm that you are on the correct pin, then voltage injection it is from here. +3VLP is generated by PU401 which you have ruled out already as far as I understand.

[kotel studios]

Injecting 3v after the PL402 (+3VALWP coil) gets me 60mA power draw. I went as far as to inject 3V 750mA onto pad 5 of the PU401 (starting with 1v 100mA) but nothing heated up. None of the main chips got hot, same for the smaller SMD caps and resistors. The PR402 resistor connecting PG to VCC isn't shorted, so it's not to blame.

I also shorted pad "IN" and "LX" together while I was measuring the resistance past PL402, but nothing changed. This is odd since the SY8208B has them shorted together yet it shorts the entire +3.3v rail to ground. This would point to an undetected fault on the IC.

I could inject 3.3V past the PL402 once I connect main 20V for testing purposes, but I still have an unresolved short which who knows what could do. Best case would be that the OCP in the mainboard would trip and stop me from powering on.