Check the source and drain pins of the first two entry MOSFETs. If 19V stops at the first MOSFET, inspect the charging IC (e.g., BQ24725, ISL88731) and check the gate voltage.
Connect the board to your bench power supply set to the laptop's native voltage (typically 19V or 19.5V). hannstar j mv4 94v0 e89382 boardview verified