: Focus on the Snapdragon 710 power management lines if the device is completely dead (no power).
However, Nokia does release the "User Guide" and "Hardware Test Manual," which contain simple block diagrams. For full schematics, you must rely on the third-party repair community. nokia 8.1 schematic diagram
(Confirm with actual schematic – this is illustrative.) : Focus on the Snapdragon 710 power management
: Locate the USB-C connector (sub-board) and the charging IC (PMIC) on the mainboard. Problems here often cause "not charging" or "slow charging" issues. model numbers TA-1099
I understand you're looking for the for the Nokia 8.1 (also known as the Nokia X7 in some regions, model numbers TA-1099 , TA-1113 , TA-1115 , TA-1131 , TA-1139 , TA-1152 , TA-1154 , TA-1157 ).