La-d401p Schematic Direct

: The schematic shows communication lines between the EC and the SPI BIOS Flash memory chip. If the laptop has stable +3VALW standby voltage but refuses to power on when the power button is pressed, checking the EC_RST# (Reset) signal and scoping the BIOS data lines ( SPI_MISO / SPI_MOSI ) will reveal if the system is hanging due to a corrupted BIOS firmware state. 3. Power-On Sequence Analysis