Trace the V_BAT line on the schematic.
Troubleshooting SIM card, Wi-Fi, or cellular network failures. Key Components and Troubleshooting Areas
Once you find a legitimate Nokia 8.1 schematic PDF:
Locate the sub-board FPC connector on the mainboard schematic. Measure the VBUS_USB_IN line. It must read 5V when a charger is connected. nokia 8.1 schematic diagram
You might be thinking, "I can just visually inspect the board." Unfortunately, modern smartphones use multi-layer PCBs. The Nokia 8.1 has a 10-layer board. You cannot see the traces on layers 3, 5, or 8 with your eyes. Here is when you need the schematic:
Inductors / Coils (crucial in power supply and RF boost circuits)
Safety Warning: Component-level motherboard repair requires specialized equipment, including a hot air rework station, a microscope, and professional micro-soldering skills. Attempting to desolder chips without proper training can permanently destroy the smartphone's logic board. Trace the V_BAT line on the schematic
Understanding the schematic diagram of the Nokia 8.1 (models TA-1119, TA-1128) is essential for advanced hardware repairs such as component-level troubleshooting, trace jumping, or replacing integrated circuits (ICs).
to ground on your multimeter, use a thermal camera or the rosin flux smoking method while injecting a low voltage (e.g., 1V to 2V) to see which capacitor heats up.
Never work on the motherboard while the battery is connected. Measure the VBUS_USB_IN line
Comprehensive Guide to the Nokia 8.1 Schematic Diagram: Understanding Your Device's Inner Workings
It shows how power and signals flow between components.