The EC (IT8987E) is the first thing that wakes up after +3VALW. Pins to check:
Look for and SYS_PWROK . These signals tell the CPU that all voltages are stable. On the LA-9412P, these are generated by the EC and voltage supervisors (e.g., a TPS3808). The schematic will show you which resistor divider sets the threshold. La-9412p Schematic
Once you download the (typically a PDF with 40-60 pages), it can be overwhelming. Here is how to break it down: The EC (IT8987E) is the first thing that
The schematic shows you what should be there, not what is broken. You still need diagnostic tools (multimeter, oscilloscope, thermal camera) to find the failed component (shorted capacitor, cracked solder joint, dead IC). cracked solder joint