Replaced the SIO (Fintek F71882FG) and the main issue stopped.

But my repairs can't ever end with just a simple fix!

Now the board powers on normally, but all it does is throw the same errorIt doesn't go away even if I plug in an 4pin CPU fan. The CMOS also doesn't hold any settings (used an benchtop PSU set to 3.0V and connected the leads to the battery terminals onboard). It just resets when I cut the mains power.

The PS/2 keyboard isn't resetting when the PC...

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...

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?

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...